Switched from 87 octane to 91

Sorry dude, but...you wish.

Hell I wish.

 

When using 91 octane Toyota rates the 4.0 as having 239 hp and 278 lb ft of torque so I'd think his estimates are closer to reality than fiction (although I'd agree that the hp estimate is likely optimistic). No shame in those numbers for a V6 though (especially the torque) and I have no complaints with the mileage given the power on tap.

I also run 91 and am averaging just over 20 mpg in mixed driving. This is on a virtually brand new engine so it will still get better.

 

If i run 87 in either of my trucks they knock and ping bad, with 91 the run like a mofo

 

Somewhat related to this thread. Yesterday I filled up with 91, had about a 1/4 tank of 87/89 prior to fill up. Today I took a trip up to Big Bear (local mountain) from sea level up to about 8k. Took highway 38 both up and down. Did very minor off roading on some trail. Took it easy on the pedal compared to my normal driving.
Best mileage so far-20mpg calculated from an excel spreadsheet and scanguage.

Other than today I don't normally see an increase and I have used 91 on a regular basis when fuel prices went down.

 

i've been running 87 since the day i got it on sept 07 and have kept records of mileage at every fillup. i live in california, where 10% of our gas is ethanol.

i ran 91 for two months back in nov and dec when gas took a nose dive. i did not notice ANY improvement....? mileage was exactly the same, ~20mpg...

you guys that are saying your getting 1-2 mpg better, are you taking into account more than one tank since you switched? cause i have gotten 21, then 18, then back to 20 on successive tanks of 87. just wondering if you actually have sufficient data when you say that you have gotten the mileage increase...

 

Research numbers, not at the tires.

Course, I'm not sure about the engine testing conditions where they garner these ratings. Could be that they're hooked up to something even more friendly airflow/exhaust flow wise when they do the lab ratings. In that case, yes, my guesstimates would be high.

 

IIRC the 4 banger does not have the same computer thats on the 6 cylinder and 4 cylinder does not adjust the timing with higher octane fuel for higher horsepower the way the 4.0 does. I think you are just wasting 25-30 cents per gallon.

 

Is there any benefit to running 93 instead of 91?


Everyone on this thread is using 91 but we don't have that around here. I use 93 and DEFINITELY notice the extra kick in my 4.0L auto. I ran about 5 tanks of 87 before switching and was averaging 15.5mpg (mostly city around the hills of western PA). I have used 2 tanks of 93 and appear to be getting 16.8mpg so far. I am tracking with a spreadsheet to get an average over 10 tanks.

I like the Shell V-Power 93 and am sticking to that.

 

the extra mpg doesn't pay for itself if you get a higher octane if you are only getting 1 or 2 more mpg.

what good things would higher octane gas do for my engine other than a little more umph (which i don't really need) and higher mpg (which the extra cost cancels out so i wouldn't be doing that to save money)

 

Yes, for the past eight tanks of 93 I have consistently gotten over 20 (20.3-21.4) mpg. Before with 87 I would range anywhere from 16-19, also making me question the consistency of the 87. The tanks I ran with premium never deviated more than around 1.1

 

At 2.79 per gallon for 87 I get 19mpg average. I would need to get just over 2mpg improvement (or 21mpg) at $3.09 per gallon for higher octane just to break even on the wallet. Not even sure what the higher octanes are going for but I figured about $0.30 more per gallon. So unless the engine is going to benefit from the higher octane, I can't imagine seeing that much better performance to justify a break even scenario in the wallet. You're definately not going to save any money at the pump because there is no way anyone will see over 2pmg improvement.

 

exactly.... that's why i was hoping someone could list some of the benefits to the engine to justify the extra cost for me

 

well, from my understanding, the ECU messes with the timing a little bit so that you dont knock (predetonate). that is the sole reason for using a higher octane fuel in a higher compression ratio engine, so that it wont predetonate. but if the ECU messes with timing, the 87 is/has been good for me!!

 

Gotcha. In that case X3

 

Higher octane fuel has more combustible material (octane) and thus tends to burn cleaner, so it could help prevent buildup of waste materials in your engine. The tighter tolerances of the refining process also help prevent dilution of the fuel with other stuff.

It won't necessarily add power (you may even lose a little using an octane higher than what your engine was spec'd with), but it probably won't subtract enough to be noticeable either. Usually a slightly higher octane rating adds a little power until you get WAY over what the engine was rated for (i.e. 93 octane in an engine rated with 85 or 87). This is because octane is essentially resistance to burn/detonation, so higher octane fuels can be maximally compressed by the engine before detonation. However, compression ratio in motor vehicle engines is set, and most 87 rated engines have relatively low ratios. Therefore, with high high octane fuel in these types of engines, you may just be making it that much harder for the engine to detonate properly, losing power because of it.

Generally speaking, it's best to get as close as possible to the octane rating the engine was researched at. V6 Taco's had their engine spec'd with 91, but all we have around here is 89 or 93. I go with the 93...I'd rather have too much combustible material than not enough. Two over is better than two under I'd say.

 

Why does the manual say to use 87?

 

Well, firstly, I can only speak to the V6 current model Tacos - the 1GR-FE engine. It was spec'd at 91. If that's what your truck is packing, read the owner's manual again - it says "87 octane or higher". 87 is the minimum.