Using 100LL (AVgas)

Someone in another thread mentioned the use of 100LL as a means to octane boost the puny octane level of 10% ethanol gas. It was kind of a mixture of topics in that thread so i figured I'd start a dedicated thread in regards to AVgas. I was wondering if any of the engine/car gurus on here would know what, if anything, adding 100LL to the the tank would do positively and or negatively to the motor???

I just so happen to work at an airport and have very easy access to the stuff and for just as cheap if not cheaper than the paying at the pump .
Wondering if it's worth the effort?

 

The pkg of detergents and other additives in automotive gas probably are not in avgas? Over time you might end up with more carbon buildup?

 

I didn't think about that, but I wasn't planning to run it exclusively but wanted some input as to whether to run like a gallon or 2 per fillup or as much as 50/50. Wasn't sure. that way I don't miss out completely on the additives and detergents.

 

You should be able to run it if you are mixing it, would be a complete waste and possibly harmful to run a mixture of 50/50. I'd very much doubt you'd see any difference in performance or power from running it though, not like these trucks were designed for high performance. Now if you were to throw a turbo or S/C setup on your truck then you may actually see some benefit from running avgas.

So all in all, probably not worth the headache and effort.

EDIT: Adding more octane to a engine does not equal more power. If an engine was engineered to run on 87 octane putting 91 octane fuel in will not gain anything but emptying you wallet faster.

 

The LL stands for Low Lead, which means it's still a leaded fuel. That lead content will damage your catalytic converters and oxygen sensors. You don't want to run any leaded fuel in your truck at any time for that reason.

Higher octane fuels will not translate to additional power unless the engine is retuned to utilize the higher octane, so you're not missing out on anything.

 

Might run the engine too hot?

 

I wouldn't think it would hold advantage long term. I'd be concerned with effects on the catalytic converter. Oh and of course not paying Road tax.

 

Forgot about the lead, yeah that would destroy the catalytic converter pretty fast.

 

The ECU has feedback mechanisms to trim the fuel mixture back in to the appropriate range. 100LL has a similar enough stoichiometric point to regular pump gas that any differences would be corrected quickly enough.

The real problem is the lead content, which will damage catalytic converters and oxygen sensors. Running any leaded fuel can get expensive quickly when you start having to replace those parts.

 

i just dont see any benefit to running high octane gas in the tacoma. isnt like its knocking on pump gas and i highly doubt the vvt is capable of utilizing that high of an octane fuel.

quick lesson on octane: higher number, higher resistance to predetonation(knocking). in a high compression engine or boosted application it can help because you can adjust timing and get more squeeze before the bang.

in a tacoma you are likely throwing money away and potentially harming your truck by running fuel with a different set of additives engineered and designed for a different application

 

Actually now that I've thought about it no, the engine would actually run cooler if anything as the engine doesn't have enough compression to fully utilize the higher octane fuel and it wouldn't fully combust.

 

I don't know where you get your info, but ethanol has an octane of 113 and it boosts the octane of gas

there is no difference in pure gas, or ethanol mixed gas, if the resultant octane rating is the same after it is blended anyhow
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furthermore

Avgas contains Tetra Ethyl Lead (TEL) - the additive which is banned in automotive fuels

you will nuke your cat converter pretty quickly if you make a habit of using avgas

 

That's not true at all. Ethanol has a very different stoichiometric ratio than normal pump gas, requiring significantly more fuel per unit of air in the mixture. This is why you can't run higher than E15 (15% ethanol) in the Tacoma.

Vehicles designed to use E85 (85% ethanol) and other ethanol blends in between will use some combination of an ethanol content sensor and fuel trim feedback loops in the ECU to compensate for the different fuel requirements.

Just don't start blending arbitrary amounts of ethanol in to your Tacoma, because that will cause major engine problems.

 

Lead + cat converters = BAD !!

 

We had an old airport truck that we'd fill with AVGAS and that sucker ran hotter than a $2 pistol

 

No, this is incorrect as well. It's true that higher octane fuels tend to burn more slowly, but that doesn't mean you need to do anything special to actually burn the fuel. Higher compression ratio isn't necessary to burn higher octane fuel.

You could argue that the marginally slower burn time could increase the exhaust gas temperature at the valves, but the increase is near negligible. That heat was going to be dumped in to your engine block and heads either way, so the truck wouldn't run hotter.

 

LOL...Stay away from 100LL, it has more than double the lead that old regular gas had in the 70's early 80's. 100LL stands for low lead compared to old aviation 100 octane which almost had 4 times as much. Not only will it destroy your converter, it will form heavy lead deposits on the valves, plugs and piston rings. 100LL is for air cooled piston engines that run high horsepower and have very sloppy tolerances compared to car engines. The lead deposits actually help lubricate the exhaust valves in those engines. In some of those engines they will run at 350 HP at 2700 RPM and have to be able to do it continuously. So you are talking high compression, power and low RPM, so they need that type of fuel.

Here is another kicker, you probably like all of us run synthetic oil. In the mid to late 1980 Mobile One came out with a 100% synthetic oil for piston airplane engines, they were almost sued into bankruptcy. Synthetic oil is great for running in clean lead free engines like our current auto and truck engines. Turned out unlike dino oil which absorbs lead and takes it too the filter, synthetic oil doesn't, so the lead builds up in oil passages and then they get blocked staving oil to parts of the engine. After many catastrophic in-flight engine failures and some fatalities. Mobile One immediately stopped production of synthetic oil for piston airplane engines. They did come up with additives that would take care of the lead, but the damage was done. To this day, piston airplane engines only run on dino oil. Ironically, synthetic oil was originally developed for jet airplane engines, and works very well, no lead there.

 

The Vapor Pressure of Avgas is totally different too as it is meant for high altitudes, and besides that it also has Lead as mentioned above.

 

How is 100LL cheaper than pump gas? Here 100LL is over $5 a gallon.

 

I'm pretty sure you are not supposed to do that. And since when is 100LL cheaper than car gas??

G.