Thoughts on Gasoline

I am a fairly new member of this forum, and have been reading a lot of posts. When it comes to the gasoline used, there is a lot of discussion regarding MPG and associated cost differences, but not much said about gasoline quality, and the long term effects from it.

For background, I am 77 and retired, with 40 years of my 52 working years in a refinery. For several years of that time, I blended gasoline, tested gasoline, certified gasoline, tested competitors gasoline, and regularly overhauled the test engines used. I have easily driven over a million miles, owning muscle cars, Broncos, Suburbans, Tahoes, various Toyota sedans, and now a new 4Runner Limited. For technical reference, I have a B.S. and an M.S. in Chemistry, having worked in various labs for 22 years (including college years). With that background, I offer the following thoughts:

* All gasoline is blended from approximately 7-8 different refinery streams into a blend header, plus a proprietary additive package. "Final" gasoline tanks are distributed (lifted) to terminals via pipelines for further distribution to retail outlets, with additives typically (but not always) added at the terminals.

* All gasoline grades are fungible, and each refinery uses blending feedstock from several different process units (via component tanks). The blend is formulated to achieve a large set of test parameters for each grade. The gasoline tank is tested at the refinery lab and certified at a third party inspection lab. Octane is tested on Waukesha single cylinder, variable compression engines. The octane value is an average of the Research Method octane and the Motor Method octane (same engine, but run at different temperatures and RPM's. They attempt to duplicate highway and in-town driving conditions of a vehicle. You end up with the final octane value (R+M/2), which is posted on the gas pump.

* The formulas used to achieve a given octane are unique to each grade. The component streams used to achieve an 87 octane are much different from an 89, or a 93. For 87, more lower octane components can be used to achieve that octane, and they are more reactive (not good). Examples include raffinate, light fluid gasoline, and straight chain hydrocarbons, such as n-butane. For 89, less of these lower quality components can be used. Examples include alkylate, heavy aromatics, and reformate. For 93, even a higher percentage of high octane components must be used. High octane components are more expensive to make and valuable to sell; therein lies much of the cost difference of octane grades. It is not arbitrary or price gouging.

* Why is all this important? With each octane grade increase, you have much less potential for pre-ignition, gum formation, and polymerization. With higher octane gasoline, you have more kcal/mole of energy generated in a cylinder cycle, which produces more force to the crankshaft, giving higher gas mileage IF all other conditions are equal. It is an absolute fact, dictated by chemistry and physics, but driving habits and driving conditions can neutralize and influence some of that advantage. That is why there is always debate on the MPG/grade calculated; too many variables.

* All gasoline additive packages are not equal, and some are far better than others. They contain compounds that reduce rust, absorb water, decrease friction, bind sulfur, and reduce polymerization. Typically, the big brand gasolines contain the highest quality additive packages. When you see real low cost, non-branded gasoline relative to that geo area, consider the gasoline components used, and the quality of the additive package. It all matters.

* Manufacturers set a gasoline octane spec for an engine based primarily on the avoidance of pre-ignition plus cushion. The higher the compression ratio, the higher the octane requirement. Higher compression will increase the pre-ignition chances in lower octane gasoline because those hydrocarbons fracture prematurely, causing premature valve lifting (clattering, knocking, etc.). For example, pentanes fracture (break apart) much easier than toluene or mixed xylenes.

* In all the vehicles I have owned, all of which I have driven to 180K miles or more, I have always used 89 octane (or higher going way back) from high quality refiners (e.g. ExxonMobile, Shell, Chevron, etc.). I've never experienced fuel system issues, internal motor issues, or exhaust system issues on any of my vehicles. I've never used a gasoline additive or treatment on any of these vehicles. The exhaust gases (CO2 + H2O vapor) are of high concentration, and the tail pipes are carbon free. (With gasoline combustion, the major by-products are CO2, H2O, with trace amounts of sulfur compounds, nitrogen compounds, and uncombusted hydrocarbons). With high quality gasoline and a well performing catalytic converter, the concentrations of CO2 and H2O are very high, trace compounds low to trace.


My point in all this is to suggest you consider more than MPG and cost. For long term maintenance free performance, consider buying gasoline from quality refiners, and using 89 (or higher) octane that requires a much higher component formulation in blending, and an additive package that best protects the vehicle from gas tank to exhaust pipe. For 4R owners, who typically value this high quality vehicle for design, flexibility, performance, and longevity, consider the value higher quality gasoline brings to your long term goals for your investment. It's much more than just MPG and cost!!

Thanks for reading and considering a wider range of gasoline criteria.....

 

I read it all.

I'm still going to the nearest station when its time to fill up.

If I cared about MPG I wouldn't have V6 and V8s.

 

I dont even read all that, as it is not important nowadays. Fill 87 at your convenience gas station, and spend your retirement time with grandkids.

 

If I didn't drive a lot, I might be inclined to use higher octane fuel and see if I noticed a difference. But, I drive way too much to spend the money on premium.

Also, having put over 200,000 miles on several Toyotas using whatever fuel was convenient, and not having had any fuel related problems, I just don't see it as an issue.

 

Maybe you didn't read it all?

 

I did. Sorry didn't address the rest of the shit.

But decided nah I'll keep doing the same.

 

@TexRunner thanks for sharing your thoughts on this. We just bought a used 4runner, hope to run it for a long time, and was wondering about gasoline.

 

Its simple, go top tier fuel. That's really it.

 

My question is, how do I know what’s actually coming out of the pump? No real way to tell.

 

I read it, I still don't think it matters. I don't doubt that 87 uses less quality additives, but I don't think it matters in these 4runners.

Lets say the 87 wears out the cat quicker by 300k miles you need replacement, if you got 20 mpg you'd burn through 15000 gallons of fuel. At a cost of $3 for 87 and $3.25 for 89, that amount of fuel would cost you $45000 and $48750 respectively. That $3750 difference can cover whatever additional maintenance I might need from using 87, and by 300k miles my exhaust might need to be replaced from corrosion anyways.

What I do know is that the 87 octane costs less money now. And no one knows just how much money using more premium fuel will save me later, or even if it saves enough money to cancel out the higher cost. The 89 would have to make it so that my cat never needs replacing, which it doesn't because the metals inside a cat get expended just from being used.

The only exception is if you plan on letting the vehicle sit, then you get whatever fuel grade doesn't have ethanol in it. Because ethanol attracts water and corrodes aluminum, and this we know.

The e-free fuel might be a better choice if the price is within a few cents of e10, because e-free does have more energy in it. But that has nothing to do with octane.

 

Vehicles are designed to run on gasoline that contains ethanol and the octane rating for the engine is what the vehicle is engineered for. It's simple.

 

I love chemistry! Fun read, thanks for the post.

 

Thanks for the read, learned some new things!

 

I enjoyed reading and while I'm cheap, I would put higher octane in a vehicle that could use a reduction in the reliability vector.

I would really like to see if you'd speak with Scotty Kilmer on YouTube. He's a well respected older mechanic and would love to ask you about additives ...

 

@TexRunner, thanks for sharing your knowledge & experience. Very interesting read. Sticking with name brand 87 though.

 

I buy 87 but the one that has additives/detergents, I like Arco rates.

 

Spot on! And this has been validated over and over again. The automakers have proven this in their prototypes and 87 just lays down more carbon over time than higher octane grades. This has been shown many times in different engines. Great chemistry read indeed!

 

Very informative and insightful article. Thank you. Question for you…

I can purchase ethanol free gas at the local Mavericks where I live. It’s available right at the pump. I also don’t have to smog check any of my vehicles in the county I live in. I would be interested in your opinions on the regular use of ethanol free fuel in my automobiles. I know its great for lawn mowers, snowblowers, and weed hackers, but what about its everyday use in an automobile?

I have noticed better gas mileage using ethanol free fuel, close to to 3 mpg increase, and more power.

 

Ethanol free gas makes no difference in smog or engines. The only environmental impact is a long disproven belief that we're better off wasting water, fertilizer, and land to grow corn to make into ethanol because it burns slightly cleaner (even if we get less energy out of it).

All engines that run E10 can run E-free. Ethanol is only used to boost octane, E-free gas uses something else (like MBTE) to boost octane.

 

Sorry too lazy to read all that..

Just pumped Shell 91OCT (I think its called VNitro). Normally pump 87 but once in a while pump 91 at Shell thinking it would clean things bit more than regular 87 at Shell. I mean I think Shell premium might have bit more detergent like chemicals. It's not too expensive here in CO. I could be wrong, just sharing what I do.

 

Do you know what really helps clean things up? Doing 65 mph for an hour on the highway. Yesterday I drove 350 miles at 80 mph, the engine stayed between 3000 and 5000 rpms. That burned everything, everything cleaned up

 

@kmeeg, unfortunately your bolded text is correct, higher octane fuel does little for an engine rated for 87. Some people claim higher mileage but seldom significant enough to offset the cost, and IIRC, it has no more cleaning properties as octane figures into fuel ignition and is not any more of a detergent.

 

87. Costco. Otherwise Kwik Trip.

All you need to know with this engine.

 

Is 89 commonly produced at the refinery? Everything I've read says it's most often blended at the terminal or at the gas station pump (50/50% of 87 octane and 91, or 67/33% of 87 octane and 93).

 

From the US Dept of Energy HERE

"Ethanol contains about one-third less energy than gasoline. So, vehicles will typically go 3% to 4% fewer miles per gallon on E10 and 4% to 5% fewer on E15 than on 100% gasoline."

 

Thanks for the post!

 

87 always

 

I could have highlighted the vNitro thing. Could be some marketing BS. But using it once in a while even though we have port injection in addition to direct. Else 90% of the time its 87oct at top-ties gas station or 91 in top-tier gas stations that doesn't have 87oct (places like Costco only has 85 and 91 here in CO).





Edit -
No matter how many times people say 85oct = 87oct at high altitude I use 87 or higher.

 

I have been using ethanol-free 91 octane forever and will continue to do so for the forseeable future. Of course, both my current and future rides require 91 octane so I'm not choosing the octane by choice. The ethanol-free gas is a conscious decision.

 

The Shell info says "...with continual use..." but one way or the other, surely this isn't the only fuel that can make such a claim. And to be clear, I don't mean to sound snarky about this.