Octane difference?

Reporting your reporting.

And 87.

 

Does the tundra state it can run on 85? I read into this last time we were in CO and it seems like 85 was more for back in the carburetor days. I guess if it isn't giving you any trouble then it's saving some money.

https://tap.fremontmotors.com/is-85-octane-ok-to-use-at-altitude/amp/

 

It's essentially 87 @ altitude. Over 5000'

They sell 85, 89, and 91 here

 

I live at 10,000 feet and run 85. It's more about forced induction that requires higher octane at elevation. I wouldn't let my wife buy a turbo MDX last month because I know she will always put in the cheapest gas.

 

I'm offering, from 14 years of personal experience in a dealership that had four different makes at one time or another, plus all the different brands we sold used, that the most common by-product of running a higher octane than your engine requires is emissions equipment failures downstream, oxygen sensors and catalytic converters being the most expensive. Would like to have a few bucks for every converter that destroyed itself due to what is essentially raw fuel being burned inside as its owner was "driving it clean" or "getting more performance" or whatever other false story they were sold by the fuel commercials. Heck, I'd just like to have the wasted money that people spent on the higher octanes rather than what was clearly called for in their owner's manual, on their fuel cap, etc.

 

Came across this at a Murphy. Didn't know they carry ethanol free gas...

 

Did you happen to notice the price difference?

 

Ethanol free 87 octane around South Carolina is typically as expensive, if not a bit more, as 93 octane w/ 10% ethanol.

 

I'd have had to pull the pump handle and didn't get that far.

 

is this station around boaters?

 

At least here the 91 has no ethanol. That's our only ethanol-free option.

 

The Murphys near me usually has the ethanol-free priced right between the mid-grade and premium to give you an idea.

 

No

 

You have got to explain this in some detail. Are you saying running higher octane causes the engine to run “rich”? Not to question you, but can you provide specific evidence as to this being true? So in most cases of emission equip failures, the owners also stated the used only higher octane than required? Wouldn’t manufacturers warn against using higher octane as it would lead to failure of emissions equip? Since many emissions components have warranty periods of up to 10 yrs the manufacturer would have a vested interest in protecting those components.

 

I don't remember the exact explanation that was given by the vehicle manufacturers' reps/attorneys but when they put it in "layman's terms" it was something along the lines of the lower compression engines were not designed to burn the entirety of the higher octane fuel in the combustion chamber so in essence, if you ran 93 in a lower compression (read "most passenger cars of the time") engine that was designed to run on 87, the unburned portion would then go out with the exhaust leading directly to significantly higher temperatures in the downstream components such as the oxygen sensors and catalytic converters. Although already reaching into extremely high temps, the converters especially would suffer from the increase. We'd see the honeycomb-looking materials inside breaking down and in many cases being blown through the exhaust and causing issues inside the muffler or mufflers as the debris collected there.

Manufacturers' reps that I dealt with were from GM (Pontiac), Chrysler (Jeep), and Isuzu and all three were involved as in nearly every case, and I'm talking in the hundreds over the 14 years I worked in the service department, the parts were still under the extended emission warranties. In most cases, the manufacturers did not have to pay for the failed components as fuel receipts provided by the vehicle owners showed that the higher octane fuel was being used while the owner's manuals and in many cases fuel tank lids, stated specifically what octane fuel to run. I was in court on a few cases and this was almost always what sealed the deal as "use 87 octane" is pretty self-explanatory. It was highly unusual to find a failed catalytic converter that was caused by much of anything else. Oxygen sensors were a little different and it was my experience that for a while in the mid to late 90s, many failed even when the correct octane level fuels were used.

ETA: above had said "80s" and I meant, and changed to "90s"

 

Thanks for the response. It does make sense at face value. I guess it is possible now that these components have been engineered/improved to withstand greater temps. Your actual experience/data appears to be at least 30 yrs old, mid to late 80s. The OM specifically states to use 87 or higher octane or engine damage could occur. Nowhere does it state using octane above 87 could/will cause damage. Maybe those other manufacturers you listed stated not to use above 87 octane? Not trying to argue, but it’s important to cite current manufacturer’s documents.

 

Point they make (and it's from 90s through mid 2006 experience, I misspoke initially and corrected in post #165) is that you don't use less than 87, maybe go up to 89 if that's all that's available, but there's a BIG difference in how the system reacts to 87 or 89 rather than 93 or even 94 octane. You're talking the difference between the engine requirements of a plain jane chevy econobox/sedan and what fuel you need in a GT350, or other high strung engines that run compression ratios well above the average. GT350 was at 12 to 1 I believe and would easily need, and be able to properly burn, 93 or higher octane fuels.

 

OK. So the V35A in the new Tundra runs at 10.5:1. Is that considered “high compression” for a modern engine? I agree a “plain Jane” vehicle may not benefit from the increased octane. What about a TT?

 

I think the V8 in mine is 10.2 but, as you pointed out earlier, technology, fuel, fuel delivery and mostly fuel management software has really changed since I was "in the business." I would imagine that any twin turbo engine is going to require some higher octane levels, even with all the fancy schmancy engine controllers/management systems.

 

I’m with you though. Not a fan of spending money unless I can gain some value.

 

What does your owner's manual recommend?

 

Interesting info. I did notice you named other manufacturers, not Toyota?

My owner's manual clearly says:



I'm also wondering how this would apply to FFV engines?

 

Ethanol is 100 octane. Octane isn't the issue with E85.

 

It states use a minimum of 87 or higher. The questions arose from stating higher octane caused emission system damage and early failure. Wanted to confirm Toyota did not say higher octanes were harmful.

 

now it gets interesting.

i'd consider 10:1 to be high for an efi. Direct injection or dancing cams can do 11:1 on 87, but i dont understand why. Direct injection can do more. But 10.5:1 and turbos seems like alot of extra stress and heat for no reason. Especially cammed for 87.

 

The Tundra TTV6 has both direct and port injection via the D-4S system. Wonder if this changes things?

 

Also, I assume the TTV6 has some sort of VVT. Wouldn’t that “help” deal with various octanes?

 

I'm still curious if a reflash or whatever can give the tundra the high test tune from a lexus for an extra 30hp or so.

d4-s really is the best of both. Port injection to wash the backs of the valves, and DI for supercruise.