Im guessing you are bone stock ?

87 octane base fuel is not e85. e85 is 85% alc and 15% gas

I think you mean 15% ethanol fuel (10% is standard where I live but I see other markets to 15%)

the car has knock sensors and is always advancing until it hears knock, then backing off. At 5-6 psi, which is stock, you really have to try hard to have a problem with 87 octane.

some things I would not do with 87 octane....
1. drive in 100 degree outside temp, with AC blasting, accelerating stoplight to stoplight wot
2. part throttle, full boost in 4th or 5th gear at 3000-3500 rpm. most risky area of the factory tune, very aggressive timing an lean fuel because the car is not at wide open throttle.

you can run 93 octane pump up to 15-20 psi, so it makes sense 87 is fine at 5-6 psi. to be honest, I don't drive much and like the extra insurance of octane. on my setup, around 15psi I usually run 4 gal 93 / 1 gal 110 race.

 

I need to update my signature, I think. My car has 264 cams, an aftermarket air intake and exhaust. I replaced whatever turbo it came with with a CT26 OEM so I think that is stock. My mechanic thinks it is making around 275 hp. You are correct; I am not running E85. I will update my post. I am running whatever mostly gas with up to 10% ethanol blend is out there.

I very rarely run over 3000 rpm. I drive in such a way to get it to upshift; once it approaches 3K I lift off the gas slightly to get it to upshift. I try to live in 2300 rpm land as much as possible. My turbo rarely spools up above 2nd gear. The only time I get in the 3000s is when I am driving across Texas at 80+ mph.

 

I need to update my signature, I think. My car has 264 cams, an aftermarket air intake and exhaust. I replaced whatever turbo it came with with a CT26 OEM so I think that is stock. You are correct; I am not running E85. I will update my post. I am running whatever mostly gas with up to 10% ethanol blend is out there.

... The crazy thing, is that since you've got 264* cams installed, and if you're running a stock CT26 at stock boost, those camshafts reduce dynamic compression enough by themselves that it's likely helped save your engine up to this point.
Any idea what your peak boost is with your current configuration? Also, what's the average Density Altitude (DA, aka air density as a measure of elevation) where you're at?

 

^ Thanks Madison. I was struggling with an emotional response to the notion that anyone with more than four functioning synapses would deliberately run a steady diet of 87 octane fucking horse piss in a Supra Turbo, and you covered all the bases eloquently.

For the record, Supra Turbo = 91 octane* minimum especially if it's been modified in any way. Basically any Toyota with a GTE engine in it should be getting 91+ octane. Can you get away with less in some cases? Yes. Is it a good idea or worth the risk to save a few bucks at the pump? No.
Can you run 86 or 87 octane in an emergency, and get away with it if you're running very low boost & are nice to the car? Yes, but really try to avoid doing this if at all possible.


*[(R+M)/2] method, which is the common method of rating octane in North America. Outside of the US, this would roughly be RON 98 or thereabouts.

 

^ Thanks Madison. I was struggling with an emotional response to the notion that anyone with more than four functioning synapses would deliberately run a steady diet of 87 octane fucking horse piss in a Supra Turbo, and you covered all the bases eloquently.

For the record, Supra Turbo = 91 octane* minimum especially if it's been modified in any way. Basically any Toyota with a GTE engine in it should be getting 91+ octane. Can you get away with less in some cases? Yes. Is it a good idea or worth the risk to save a few bucks at the pump? No.
Can you run 86 or 87 octane in an emergency, and get away with it if you're running very low boost & are nice to the car? Yes, but really try to avoid doing this if at all possible.


*[(R+M)/2] method, which is the common method of rating octane in North America. Outside of the US, this would roughly be RON 98 or thereabouts.

lol Im at the total opposite end of the spectrum as OP. like my car is never below 3000 rpm unless im idling at a light.

I hit 6000 rpm every. single. time. I. drive. it.
no exceptions. 99.9% of my time driving is spent in a prius. I get in the supra for one reason -- to hear my turbo scream and rip some pulls to redline. to each their own I guess.

 

If I could trade my 7M-GTE drivetrain for a 7M-GE I would do it. I have no need to go fast. I bought this car for open road cruising 500 miles a week. I would have preferred a stock vehicle but this is how it came. The body and interior are in great shape so I had to take the engine it came with.

 

Either way, you're going to put the right fuel in it from now on, right?

 

Given my pedestrian driving, unless the TSRM says differently I am using 87.

Regarding density altitude, my house is 50 feet above sea level. My office is 13. I can be standing in the ocean 45 minutes drive from my house.

 

I have 7m GE.. the only fuel I need to run is 87 correct ? Or can I use non ethanol? I also thought about running mid grade even though I am all stock..

 

Ok. I just drove the 55 miles to get home. I have a digital manifold pressure gauge in the car. Twice it got to 4 psi as I accelerated from a stop but dropped immediately when it shifted up. I rarely let it rev enough to even hear the turbo spool up. Driving 65 I pressed the gas all the way to see what it would do and it topped out at 8 psi. Most of the time it was reading -10 to -8 inHg.

 

I also found it strange no minimum octane rating in fsm. Just says "only unleaded gas" i have a stock 7mge and pump 91octane. I like to feel thats the right thing to do

 

@fintable...
Depending in you area, if prices follow

87 = 3.09
92 = 3.59

That is $10 dollars per tank delta (yes estimating 20 gallons and not the real 16 gallons on refuel).

Or better yet, that is;
1.75 x starbucks
2.25 x happy meals
1.2x dbl 1/4 pounder with cheese meal at mcds or most any fast food joint
5 9x 20oz soda at the gas statiion

The bad news for you, the oxygenated fuel will hinder mpg just by the sheer nature of having oxygenation in the form of Ethanol

Also the further bad news is that you are a battery replacement away from the stock tccs forgetting all the learned knock values.

The manual was written in the 80's. Oxygenated fuels were not in the pumps yet.

Just pony up the cash for 91/92.

 

I drive 500 miles per week and have to fill once on Sunday and once during the week. I will do some A/B testing and see. I drive to maximize mpg, doing things like drafting behind an 18 wheeler. I’ll do a couple weeks worth of each and report back.
On another note, down here Buc-ee’s has ethanol free gas. I will see if I can get that and also do a $/mile comparison.

 

On my 88 turbo I went from the factory computer to aftermarket, sequential injection with modern injectors (WRX STI pinks), sequential ignition and slightly lean burn cruise (15.3:1 AFR) and I'm getting 8.4L/100km cruising at motorway speeds (~100-120km/h). That's 28 US mpg. Tuned for E5 95 european fuel, so E5 91 octane american.

Might be worth investing in a modern engine management system.

 

...
i really dislike when people ignore simple science to try see for themselves... oh well!

 

I know for my MR2 turbo, premium fuel is required, so I use that. I don't have the owner's manual for my non-turbo Supra in front of me, but if I recall correctly, it recommends premium for optimal performance, and because it's not just some beater Camry I don't give a crap about and is something I want optimal performance from, I go with what the manual recommends.

 

@sinistar_xx use premium fuel in the non turbo? will the shop manual tell you what to use as well ? because i have that in front of me now

 

I also use premium in non turbo, my fsm dictates "unleaded fuel only" no minimum octane rating.

 

With what we know of the TCCS thanks to @3p141592654 and the massive undertaking of decompiling the stock TCCS.

In the MA70 Turbo. the TCCS will always push timing until knock then pull back and record where it found the knock threshold and store it. If the battery is disconnected it has to relearn that. If it stores the knock values based on 87 vs 91. The total power output will be LOWER since it is taking timing away which means less power at a certain throttle input. (3p, correct any sloppy info)

Lower power output means less MPG (regardless of fuel).

So technically, you want fill car up with the highest octane you can afford, disconnect & reconnect battery and let the TCCS learn the knock value using 91 octane. That will allow the car to run the most efficient ignition values available to it.

 

@Suprabruhh ohhh ok understood that will be my next fill up .. http://www.supramk3.com/manual.pdf see page 197. i you are right guess i need to start doing that

 

My understanding of piston engines is that octane indicates the propensity of a fuel to detonate under pressure. The higher the octane, the higher compression it will tolerate without preignition. I rarely run my car with rpm's sufficient to spool up the turbo, and my 264 cams delay the closure of the intake valve, thereby reducing the compression in the cylinder. Premium fuel existed when this car was new; my 1986 SAAB 9000 Turbo ran better with higher octane fuel but being a 2.0L Turbo the car was almost always using boost.

I filled up my tank this morning. I will be tracking the cost per mile for the next several weeks using 87,89 and 93 octane gas from the same gas station. I will report the results in a separate post.

According to that link I am supposed to use 97 octane gas. My local station has 87, 89 and 93 so I am not sure how to interpret those numbers.

 

Finaltable, as Chocolate_Cowboy has referenced from the Supra Handbook as per pg. 197.

SPECIFICATIONS
Fuel

Fuel type:
7M-GE engine:
For optimum engine performance, Toyota recommends using premium type unleaded gasoline
with an octane number of 95 or higher (Research Octane Number). If such premium type cannot be obtained, you may use unleaded gasoline with an octane number as low as 91.
7M-GTE engine:
Unleaded gasoline with an octane number of 97 or higher (Research Octane Number).

The RON 97 Octane does coincides with what Wreckless said earlier in the thread, which means PREMIUM fuel is specified.

Also, FWIW. I drive like a putz in my Corolla (Corolla #1), but noticed the car fell flat on its face when ambient temp was > 85*. I started to think about it, and realized the ECU must be running LESS efficient when temps are higher because the ECU is pulling timing due to the 87 Octane and higher intake temps. I switched to 93 octane thinking it would help with knock and improve efficiency I and haven't looked back. I got 6 more mpg and cleaner oil. For all the engine pros here on SF, they may think I'm crazy, but I got longer oil change intervals as per what my ECU was reading. I don't know how exactly, but the ECU knew the oil was cleaner, and it started to get more miles per oil change. I still kept the 87 octane oil change interval for peace of mind. With 93 Octane the ECU was "giving" me 1200 miles difference. Also, the oil that came out for oil changes went from thick and black with 87, to smooth and brown like honey on 93. In my "new" Corolla (Corolla #2), I tested it again. When I switched from 87 to 93, it got 7+mpg more than on 87. Again, the engine is running more efficiently and netting more MPG with a more efficient running engine. Toyota says the Corolla is made to run on 87, but my experience/observation and conclusion is that it is most efficient and optimal with 93 Octane. 93 is the only way to go IMO, even if I'm not driving aggressively.

 

The stock ecu can hear knock and retard timing on the next cylinder event so it is fast.

I didn't drive my supra to work today but I know that Toyota recommends premium but they do not require it.

 

It turns out I should have just looked in my glove compartment because it is right there on the cover of the owner's manual. 87 is acceptable, higher is recommended for improved vehicle performance.

It seems it is perfectly safe for me to continue my test and will not hurt my car to use 87 octane gas.

 

First things first - that book was published before ethanol/oxygenated gas existed. Octane requirements generally went up across the board because of this. OEM's tuned engines accordingly, but old manuals for old cars are no longer accurate for all the reasons @figgie explained.
Second - you no longer have a stock vehicle. Your driving habits have mitigated a lot of the potential risk, but don't eliminate it.

That does make me wonder how much of the original BHG issues in 7M-GTE's were from people just running 87 octane, especially after Ethanol was added. Occasional mild detonation is a great way to kill a composite HG over the course of 40-50k miles

But given your preferred driving style, It got me thinking about the ideal engine swap for that kind of thing. It's impossible to deny that a MKIII is an excellent long-distance cruiser. I always enjoyed that paired with a shitload of horsepower but the horsepower isn't necessary to enjoy that cruiser aspect of it.

Easy button would seem to be a 1UZ-FE from a SC400 complete with auto trans - reliable as hell, lots of low end torque and easy power without hitting MPG in the shorts, but it also requires premium.

That got me thinking that a 4.0L 1GR-FE and 5AT auto from a 2WD 4Runner or Tacoma would be simply perfect. Lots of low end and midrange torque, good throttle response, insane reliability, drinks 87 octane happily and all day. The 5AT auto would help daily driving/mpg as well.

 

First things first - that book was published before ethanol/oxygenated gas existed. Octane requirements generally went up across the board because of this. OEM's tuned engines accordingly, but old manuals for old cars are no longer accurate for all the reasons @figgie explained.

There is a chain of gas stations called Buc-ee's in my region of Texas that sells ethanol free gas at most of its stations. I plan on trying that as one of my options. There is a station very convenient to me on my commute I can use. I just need to make sure I time fill ups because it is halfway between my house and work.

 

If I ever have to do a complete engine replacement I am leaning toward the 1UZ. I found the guy in New Zealand who has done 20 of these swaps and he sent me a trove of info on it. I have already discussed it with my uncle/mechanic and after reading all the info he says it doesn't sound any worse than what we have already done rebuilding the 7M and replacing the A340. I kind of want to not spend money on the car right now given that I just replaced or rebuilt the entire drivetrain. I didn't know the 1GR was an option. I will look into that as well and appreciate you telling me about it. Next year I will start looking for all the parts needed for a swap and sending them to the shop as I find them. I am only 50 and expect to be at this company, doing this job, for at least another ten years. At 25,000 miles a year I harbor no illusions that this car is not going to need some major work at some point to keep going.

 

Buc-ee's is a national treasure. I wish they'd build some in NM.




The 1GR is a hypothetical option, I'm not aware of any running MK3 swaps with a 1GR-FE. I do know that 2GR-FSE has been swapped into Toyota Altezza (IS300) and Toyota Soarer (SC300) chassis in Japan, so I'd imagine the 1GR could work though the truck vs car accessories and manifolds and such may change that. So there's some 'pioneering' and figuring out to be done as to how difficult/time consuming it would be to swap effectively. The 1UZ-FE is definitely an easy and straightforward swap, and it does okay on mid-grade gas, but 86-87 octane makes it hate life and I can speak to that having owned an LS400 and SC400 in the past, and I put probably 70k miles on the LS400 in my ownership.
So if you're open to running mid-grade as a minimum, the 1UZ-FE is a drop in proposition if you find an LS400 donor. There's the wiring and all to handle but the engine mounts and trans mounts, trans linkage, gauge cluster, etc are all fairly straightforward to sort out in a MKIII. For your highway mileage, I'd say dropping to a 3.58:1 final drive at the same time as the 1UZ swap would be an excellent call as well, though getting the speedometer accurate would be a little troublesome.

....Now that my brain finally started working, I'd say nix both of those and go with a 2UZ-FE out of a Tundra instead. Similar 4spd auto, but drinks 87 octane all day long and it's torque for days. Similar packaging and swap parts required, one could use the SC400 oil pans and exhaust manifolds on the 2UZ-FE and just sort the rest out from there. It'd weigh a little more being an iron block, but it'd make more torque and drink the cheap gas.

Interesting thought, Wreckless. I've been running 89 octane since my 2nd BHG because the head lost a fair amount. My GE does knock mildly and briefly sometimes when I'm shifting quickly from high revs. I attribute it to the pokey ECU processor not being fast enough to keep up. My 3rd composite gasket died in 60k miles. Surely, the regular mild knock didn't help, but I still completely blame Toyota for a piece of crap gasket.

I will suggest a regular addition of Sta-Bil to keep the stupid ethanol from causing trouble.

And, I've seen a Supra with a 1UZ-FE and it was awesome. Talk about a lot of work, though, including a custom steering rack.

LS400 and GS400 1UZ's are front sump and definitely would not fit a MKIII without lots of changes to the steering etc. But an SC400 1UZ-FE has a rear sump oil pan and much more compact exhaust manifolds, and swapping one of those into a MKIII is very straightforward these days. Basically it's just engine mounts, wiring, and bolt the damn thing in, then finish the exhaust etc.

 

Interesting thought, Wreckless. I've been running 89 octane since my 2nd BHG because the head lost a fair amount. My GE does knock mildly and briefly sometimes when I'm shifting quickly from high revs. I attribute it to the pokey ECU processor not being fast enough to keep up. My 3rd composite gasket died in 60k miles. Surely, the regular mild knock didn't help, but I still completely blame Toyota for a piece of crap gasket.

I will suggest a regular addition of Sta-Bil to keep the stupid ethanol from causing trouble.

And, I've seen a Supra with a 1UZ-FE and it was awesome. Talk about a lot of work, though, including a custom steering rack.

 

I've always run 91 octane in my 7M-GTE. Today that price is $4.85 a gallon at my local Chevron.

 

Ouch! 87 is $2.79 at Buc-e's. 93 is $3.33. Plus I get $0.10 off per gallon by having a TDECU credit card.

 

@finaltable I miss Buc-ees! I grew up in Austin and stop by whenever I'm visiting family in TX. No such luck on gas prices here.

 

Georgia has two Buc-ee's one in the northside of the state and one on the southside of the state