Toyota Tundra Forum

NO MORE Z71 · #61 (**permalink**) 08-16-2009, 02:55 PM

Quote:

Originally Posted by rarjar

Makes perfect sense to me Cabby, lol!

Me too...!!!

My1stTundra · #62 (**permalink**) 08-17-2009, 09:51 PM

I have heard three things about gas:
1) If the manufacture suggests using 87 octane, then, using 89 or 91+ octane gas has not been in the design considerations. The valve train, ignition timing, compression ratio, air intake, exhaust, temperature and density, motor oil, even gas spray pattern, etc. all plays a role in the engine function. If it is designed to use higher octane, the engineers will optimize all the factors. This is why the similar Toyota 3.5-liter V6 engine has different output between Camry and ES350 (87 versus 91+ octane).
2) If an engine were new and used higher-octane fuel, the engine metal/alloy would set wrong. So when the engine is older (say 80K or 100K miles later), the engine will not be able to use 87 octane without any 'knocking''. So, do not waste money on 'improve the engine' by higher-octane fuel.
3) The oxygen generator, i.e., ethanol, has less energy. The octane 89 fuel has no additional total energy per gallon. The only difference is we may get the 1% to 2% less loss between 87 and 89 octane. The 91 and above can only has 2 to 3% less lost. It is too little to make any significant difference.
The engineers know much more than we do in the engine/fuel technologies. On the other hand, I have been told and experienced to slow down, smooth start and stop will improve the mpg.

LeaveB3sbehind · #63 (**permalink**) 08-19-2009, 11:37 AM

Quote:

Originally Posted by My1stTundra

I have heard three things about gas:
1) If the manufacture suggests using 87 octane, then, using 89 or 91+ octane gas has not been in the design considerations. The valve train, ignition timing, compression ratio, air intake, exhaust, temperature and density, motor oil, even gas spray pattern, etc. all plays a role in the engine function. If it is designed to use higher octane, the engineers will optimize all the factors. This is why the similar Toyota 3.5-liter V6 engine has different output between Camry and ES350 (87 versus 91+ octane).
2) If an engine were new and used higher-octane fuel, the engine metal/alloy would set wrong. So when the engine is older (say 80K or 100K miles later), the engine will not be able to use 87 octane without any 'knocking''. So, do not waste money on 'improve the engine' by higher-octane fuel.
3) The oxygen generator, i.e., ethanol, has less energy. The octane 89 fuel has no additional total energy per gallon. The only difference is we may get the 1% to 2% less loss between 87 and 89 octane. The 91 and above can only has 2 to 3% less lost. It is too little to make any significant difference.
The engineers know much more than we do in the engine/fuel technologies. On the other hand, I have been told and experienced to slow down, smooth start and stop will improve the mpg.

Welcome to the club since I haven't said hello yet!

In most vehicles its true.......however

1.) The Tundra's 5.7 and 4.6 are the best, the engines adjust the air/fuel mixture. In the manual it clearly states "MINIMUM 87 Octane". Key word MINIMUM.

2.) See #1
3.) See #1 and I have found running 89+ Octane gas that the truck drives alot better. Smoother and accelerates faster w/ less gas. I towed a few times and the last 2 trips I followed a members advice and used 91 Octane, my mpg went up 1.4 with 91 vs 87 on the same route.

lymerock · #64 (**permalink**) 08-29-2009, 10:01 AM

has anyone hooked up a scangauge to monitor timing?
Id be willing to bet timing advances when running higher than 87 octane.
most new engines run multiple maps based on many factors from temp to load to measured octane, so getting the engine in the happy spot will effect performance.
imo advancing timing should increase mileage a bit, but perhaps not enough to be noticable.
I would love to lean out the fuel tables. with 4 cats on my exhaust I know toyota is going to run it rich so that they can meet the cat warranty by prolonging its life via a/f enrichment. if we can get control of cam timing and a/f we can get the mpg way up there.
unfortunately I havent seen any off the shelf tuning solutions but im going to keep looking.

milesss · #65 (**permalink**) 09-22-2009, 11:18 AM

This gas cap problem was told to my wife that it and the windsheild motors were not covered under warrenty on her 07 Rav 4 and it includes my truck.

Im thinking about going to a GMC dealer and see how bad they might want to trade my truck for a crewmax 4x4.All the little surprices and unpredictable mpg has got me thinking that the old days when I kept my last toyota 86 4x4 for 14 years are gone.Who knows what might happen if the tranny has a major problem that wasnt covered.My wife just had a new evaporator canister put in for free with the dealer saying toyota had found a defect in the Rav 4 canisters but if it had been a gas cap problem it wouldnt be coverd and cost 76 dollars.Im about sick of 40 grand truck and cars having chopped up warrentys.Also my truck had to have a new starter put in at 15,000mi,I never put a starter on my 86 toy.

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