Higher MPG with Premium gas?

In the end it's a matter of what is most cost effective. I suppose if you are convinced that higher octane 91 or 93 higher cost at the pump will save you $ in maintenance cost in the long run it makes sense - so far I am not convinced of that. Or if you believe the increase in MPG off sets the additional cost of the higher octane then that makes sense - although I am not convinced of that either. There is a third choice 88 E15 which is 15% ethanol and works the problem in reverse - slightly less MPG (2% decrease) at significantly less cost. From a cost effective stand point this will be cheaper (88=$2.47 vs 87=$2.67) and "supposedly" any vehicle after 2001 that runs 87 can run 88 . . . . . I will take a pass on 88.
So, yeah, I guess I will stick to 87.

EDIT: well for fun I asked ChatGPT . . . . I may just change my opinion.
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Engine Details:

• The 2GR-FKS V6 uses both direct and port injection (D-4S system).
  
  
• It has a high compression ratio of 11.8:1, as you mentioned.
  
  
• Toyota engineered it to run on 87 octane, and that’s what the owner’s manual specifiesas the minimum recommended fuel.
  
  
• For Best Performance:
  Even though 87 is acceptable, you’ll likely get better performance and efficiency using 91 octane (premium). Here’s why:
  
  ✅ Why 91 May Be Better:
  • The engine has a knock sensorand will retard timingon 87 to prevent detonation. That reduces power.
    
    
  • Using 91 allows the engine to run more spark advance, making full use of the high compression ratio and increasing horsepower and throttle response.
    
    
  • You may also see slightly better fuel economy, enough to partly offset the cost difference in some cases.
    
    
  • Why Not Always Required:
    • If you're just doing normal driving and want to save money, 87 is safe and supported.
      
      
    • But for towing, driving in hot weather, mountain driving, or just wanting sharper throttle and better responsiveness — 91 will give a noticeable (though not massive) improvement.
      
      
    • Summary:
      • Minimum: 87 octane — safe and acceptable.
        
        
      • Recommended for best performance:91 octane (especially under load, towing, or in hot climates).

 

Gas out of the pump won’t have a precise octane level on a tank fill. Probably a range of closeness is all you can expect from a busy gas station. My opinion thoughts are that a fill at an 87 pump would get you somewhere in the range of 86 to 88. But I’ll bet lots of opinions on this topic. Not sure it is worth cost to pay more for chance at better performance.

 

Yes butt dyno says 91 is better and.....

Did work commute on 87 and then drained tank did work commute on 91 (mainly surface streets some freeway). (Also ran a couple tanks at each grade)

91 picked up 2-3 mpg's and more than paid for itself. When I ran the calculations (2022, it was about $0.05/ mile cheaper to run 91 octane)

 

Don't forget 2gr-fks has Atkinson cycle, which reduces the compression.

 

My understanding is the compression ratio isn't changed, it's the expansion ratio after ignition during the power stroke that's increased. Regardless the Tacoma isn't fuel efficient or powerful.

 

That's not causing the burned valves. They're either not seating all the way or have a seat issue.

 

It’s designed to run 87 or better. Won’t burn valves. In mountain areas, we can run 85 no problems.

 

“can contribute to pre-ignition potentially leading to burnt valves.”

 

Well I am on the fence now . . . . I am going to try 91 for a few tanks and see for myself.

 

I have been using Shell 93 since 23 on my 2022. I had transmission shudder for 8 months until I switched. The shudder went away and my gas milage improved. I was at around 8000 miles when I made the switch. It could be a total coincidence as the truck and transmission may have learned my driving habits. Every truck is different. I feel it is worth it in my situation. I get 23-24 on a total stock SR5 2wd. BUT, I live in the flat lands of SW Georgia.

 

93 costs 80 cents to $1 more around here. It would negate the negligible MPG savings and only measureable on a dyno power increases.

I've tried 93 for 3 tanks and spent $20 more per tank mostly to satisfy my own curiosity.

 

Several years ago, I could get premium for around 30 cents/gallon more than regular and I used it in all of my vehicles for about a year. I couldn't tell any difference in fuel mileage, but there was a noticeable gain in power. Especially when towing. I found that it took at least 2 fill-ups to note any difference. Unless you completely drain the tank, you have a mix of premium and regular until at least the 2nd, maybe the 3rd fill-up and it takes the trucks computer a while to adjust. For that reason, I just used it all the time.

At that small price difference, I felt the small gains in power were worth it. But after about a year we hit one of those fuel price spikes and it was no longer worth the cost for me. Today the price difference is closer to $1/gallon, and I've not revisited premium.

Ethanol vs 100% gas!. In theory I understand that the 10% ethanol that I use most of the time isn't supposed to be as efficient. But I'd have to show a lot of digits to the right of the decimal point when figuring my fuel mileage to prove it. I can't tell any difference. In fact, the times I've filled up with 100% gas the truck ran poorly. I believe that since they sell so little of it the gas tends to be old.

Above a certain altitude they sell 85 octane as regular, 87 as mid-grade, and 91 as premium. I've driven a lot of miles on 85 octane and never had an issue until I tried it pulling a trailer. I filled up in New Mexico with 85 octane and really struggled up the 1st mountain pass above Raton. At 7000' on a very slight incline the truck wanted to run in 2nd and 3rd gear and the truck ran hotter than normal. We got into a campground, and I ran out most of that tank without the trailer. I filled up with 91 octane premium and had no more issues the rest of the trip.

 

Past couple of weeks have noticed a bump in mpg's. I have noticed warmer weather gives them but was wondering if the summer gas wasn't part of it too?
This is the second summer I have owned my vehicle so I'm more aware of things. I regularly travel long distances so mpg's are important to me. Winter trips are harder to get the mileage as opposed to summertime. I've become addicted to the instant mileage gauge which has allowed to get my best results.
Just did two 139 mile trips this week and got 25.7 and 25.9 mpg. It was way easier to accomplish this compared to winter where I would be lucky to get over 23 for the same trip. I only use regular gas.

 

You have any evidence to support this is?

 

What evidence do you have that says otherwise?

 

Yes! I've owned two identical Tacomas since they were new. One I only filled with 87, and one only with 91. I drove them both the exact same amount in the exact same places. The one with 87 is constantly misfiring.

 

Well, to be fair. It IS an island. I imagine the costs of shipping stuff (including all the equipment for setup and maintenance of the fuel industry in an island) can get hefty.

 

But, with everything said on the topic, I think everyone's making a bigger deal out of it than it is.

The manual says 87. 87 will serve you fine. The way the engine is designed you might notice a mild performance boost with 91, if you're sensitive to those things. Doing it to save the life of your engine is silly, these are Tacomas.

 

Yes, knock sensors. The ECU will retard timing to prevent knock when the sensors detect it.

 

It’s not a fail safe system.