Higher MPG with Premium gas?

I've never cared about mpg since I bought the truck, it has ~75k miles now, almost due for oil change. I accidentally filled up with #91 gas over the weekend. 2019 6MT DCSB TRDORP.

I normally got around 17mpg just daily driving, 18 on a good trip. I just noticed this tank is showing 21.7mpg. Not sure this is true or a fluke. I thought it is a myth.

Anyway, I will find out tomorrow when I refuel.

 

Results may vary

 

So it's possible with these trucks. The compression ratio is really high 11.8:1 which typically requires higher octanes than 87. I have considered looking at the timing on my OBD scanner and comparing the two octanes.

 

No. The energy in BTUs in a gallon of 87 octane is identical to the BTUs in premium higher octane gasoline.

And those who say they detect a difference in mileage between regular gas and gas with 10 percent ethanol are fooling themselves. It's true that ethanol only has 65 percent of the energy in gasoline so it's only a 45 percent reduction in ten percent of the fuel

 

I have been using 93 octane since new and I average 23 to 24 mpg.

IMO running 87 octane in these high compression engines is what’s causing a lot of members valve issues again that’s my opinion.

 

I'm running 32" tires.

 

Filler up with Jet A.

 

The opinion has no basis.
87 since day 1. Had same mpgs. No issues with valves

 

I bet you would get higher MPGs. But if you do the calculations, the added cost isn't offset by the gains.

Premium costs ~20% more and will not result in 20% mpg increase.

 

If ethanol has reduced energy density, there is no way you will see the same BTU's as non-ethanol (91 octane is non-ethanol in most parts of the country).

 

As I said it’s an opinion I’m entitled to mine same as you are although yours was unsolicited!

 

I'm not saying it's worth it, just an observation. In my area the difference is more than 20%. I only get fuel from Sam's and Costco. Today regular is $2.69, Premium is $3.69.

 

Frick man. Hawaii gets bent over so hard on gas. Current average is $4.59 for regular. Damn

 

I track my fuel economy pretty regularly. Decided recently to fill a few tanks back to back with ethanol free vs the normal 87 unleaded. Saw absolutely zero difference in fuel economy. This is a stock truck, no mods, original tires and wheel sizes.
I was a bit bummed because it was $0.80/gallon more expensive!

 

I get better mileage—similar to OP’s observation. I attribute it to the improved drivability at low rpms. I think this is only a thing for manual transmission vehicles

 

With modern engines it’s possible to get small gains in efficiency with higher octane fuel, because they can adjust fuel-air mixture, spark advance, etc. based on knock detectors. However, it would likely be hard to measure the difference with any statistical reliability and the extra cost of high octane fuel would likely out do the gains in fuel economy.

Feel happy your truck accepts cheap fuel unlike a Lexus. Spend the savings on your significant other.

 

2gr-fks is designed to run on 91 Research Octane Number. Which is the same as US 87

 

You pay for those MPGs at the pump, not worth it imo

 

I believe the Lexus versions recommend 93. I don’t know why, but I thought maybe they have higher compression or other mechanical difference that firmware can’t solve easily. It could also just be a marketing decision.

The Lexus versions are also rated for more output. Not just the fuel? Idk.

 

Damn! I always cited 91 research on threads like this