Way OT: Sales guy tells me to NOT run premo gas in small engine?

david n · Oct 28, 2021

So talking to a mfgr of a piece of outdoor power equipment.............has commercial Kohler engine. Says they have customers with engine issues. He tells me the common denominator is because they are runnin' premium instead of 87 octane???? HUH??? Tells 'em to run 87 and stabil.................huh? Every single small engine guy I have ever talked to recommends 91 octane...............am I missing something? Sales guy sends me this article.......................?????? I think a vehicle and a small engine might be a bit different....................... :skep:

If My Car Recommends Regular Gas, Is It Good to Use Premium Occasionally? | News | Cars.com

mattthemuppet · Oct 28, 2021

the octane no. is just the antiknock rating. The higher the compression (esp. on turbos), the higher the octane needed to help prevent detonation. Cars have had knock sensors and the like for decades, so you can run lower octane fuel in high compression engines at a lower power output. Usually the only downside to running higher octane fuel than needed is the cost. I can't imagine relatively low compression small engines like you'd find in outdoor equipment would need anything higher than 87 octane, though I can't see why that would hurt them if you did.

EmGo · Oct 28, 2021

david n said:
... they have customers with engine issues. He tells me the common denominator is because they are runnin' premium instead of 87 octane???? HUH??? Tells 'em to run 87 and stabil.................huh? Every single small engine guy I have ever talked to recommends 91 octane

Should run what it's designed for. Lower octane rated fuel has more energy. Higher octane starts to burn in a narrower temperature band, that's why you need it with higher compression. At higher compressions you don't want it kicking off too soon, preignition destroys pistons.

I can't think of how higher octane fuel would hurt an engine, but could be possible. But running hi-test in an engine that doesn't need it is definitely a waste of money and you'll get less work out of it.

eKretz · Oct 28, 2021

He's full of shit. Ethanol is the more likely cause of the problems.

david n · Oct 28, 2021

eKretz said:
He's full of shit. Ethanol is the more likely cause of the problems.

Exactly what I was thinking................anything that sits even for a week or two that has ethanol in the tank will have issues..................

johansen · Oct 28, 2021

I don't know what it does to the octane rating for sure, but ethanol increases it afaik.
You only have to add half an ounce of water to a gallon of gas, and the water will pull the ethanol out and it will settle on the bottom of the tank after you shake it up. I do this for chainsaws and other small engines.

I am not sure I would run such gas in a car engine, but a 6 or 7:1 compression ratio small engine is not going to knock.

dalmatiangirl61 · Oct 28, 2021

david n said:
Exactly what I was thinking................anything that sits even for a week or two that has ethanol in the tank will have issues..................

I think the problem with ethanol fuel is tied equally with the humidity. I run regular pump gas in several pieces of equipment out here in Nv, there have been no problems with letting things sit for a year or 2 with gasoline in them, cannot say that about equipment in Tx.

eKretz · Oct 28, 2021

dalmatiangirl61 said:
I think the problem with ethanol fuel is tied equally with the humidity. I run regular pump gas in several pieces of equipment out here in Nv, there have been no problems with letting things sit for a year or 2 with gasoline in them, cannot say that about equipment in Tx.

That is probably true. The problem seems to be worse in climates with high humidity or lots of fluctuation like frost and cold/hot cycles where there's lots of condensation.

henrya · Oct 28, 2021

Good fresh non-ethanol gas.

87 is fine as is any higher octane which mostly for this device just costs more. Its the ethanol to stay away from.

FredC · Oct 28, 2021

One mechanic suggested we run premium in our old single cylinder pump engines (Rural fire trucks). The idea was the additive package would have better stabilizers to keep the fuel fresh longer since we sometimes go months with out having a fire.
That was his opinion and he could be all wet. Since went back to regular with no difference observed. RPM is so low speed of the fuel burning has no real consequence.

CarbideBob · Oct 28, 2021

What are the additives in premium now with lead out of the equation?
As I understand it the ethanol content the same at a normal pump.
Everyone says old gas is bad. My experience with 5 year old gasoline very different.
For sure letting a carb dry out is a oh-poop but that problem goes back into the 50-60s.
I try to start and run a tad every 6 months which saves carb teardown and rebuild.
The boat with 13.5 and shaved higher is not happy with any normal pump premium now so race gas or additives in a bottle that I have no idea what.
Race gas hard to find and additives expensive.
On street cars one used to go to the airport for a fill up but that no longer allowed.
Everyone hates ethanol yet if you have run a alcohol car it is so nice. Everything stays so clean, motor life is way much longer.
Earlier aged stuff and the rubber does not like is, fuel lines get soft and collapse. Orings not happy.

And then there is summer and winter gasoline. Who would of thought that it varies over the seasons.
Bob

Gordon Heaton · Oct 28, 2021

Around here, the only ethanol-free gas I can buy is 'premium'. All my small engines get it.

PackardV8 · Oct 28, 2021

dalmatiangirl61 said:
I think the problem with ethanol fuel is tied equally with the humidity. I run regular pump gas in several pieces of equipment out here in Nv, there have been no problems with letting things sit for a year or 2 with gasoline in them, cannot say that about equipment in Tx.

For true. Those with newer equipment in dry climates have very few problems with 10%ethanol. Those with older equipment in very humid climates have nothing but problems.

jack vines

CarbideBob · Oct 28, 2021

Gordon Heaton said:
Around here, the only ethanol-free gas I can buy is 'premium'. All my small engines get it.

Is it premium at the normal pump or "RV/off road" gas at a special pump off the side?

3t3d · Oct 28, 2021

The Ugly Truth Why Gas Station Fuel Is Bad For Small Engines - YouTube

Mark P. · Oct 28, 2021

Any non-ethanol here is 91 octane

I have a 20+ year old Echo back pack blower (commercial grade)that runs fine and has only been serviced twice. When I bought it, the independent dealer told me to run Marathon gas. Which I did...it has ethanol (just found that out this year)

My dad gave me his Craftsman power washer. It quit running because the carburetor. had so much sludge in it.

EmGo · Oct 28, 2021

If you are near a place with fuel docks, most boat gasoline doesn't have alcohol. Of course it's $4.50 a gallon, too ... but maybe mileage is not a problem for small engines ?

Gordon Heaton · Oct 28, 2021

CarbideBob said:
Is it premium at the normal pump or "RV/off road" gas at a special pump off the side?

Its at the normal pump, but only at select stations. In my town of about 100,000 people I'm aware of only two stations that carry it. One of them is a Maverik, the other is a family-owned fuel depot. The pumps are clearly labeled ethanol free.

hvnlymachining · Oct 28, 2021

If you're looking for truly stable fuel with a true octane rating, use aviation fuel, 100 no lead ( used to be low lead until recent years compared to auto fuel) will not varnish ever since it is pure petroleum without addatives. We used to run it in everything but our cars ( which reminds me, I need to make a trip to the airport). You'll be surprised how well your small engines run on it. Many of the loggers and snowmobilers around here run it exclusively.

Tonytn36 · Oct 28, 2021

Gordon Heaton said:
Its at the normal pump, but only at select stations. In my town of about 100,000 people I'm aware of only two stations who carry it. One of them is a Maverik, the other is a family-owned fuel depot. The pumps are clearly labeled ethanol free.

Here in Tennessee, most Co-ops carry non-ethanol fuel and well as select gas stations, some of them mom-n-pop but some larger chains like Weigels. I run non-ethanol in my cars because i get much better fuel mileage. 2008 Altima 2S 4 cylinder, Non-ethanol 87 octane = 31 mgp on my weekly 300 miles to/from work. Regular 87 octane w/up to 10% (walmart) - 26.2 mpg, Regular 87 octane w/up to 15% (food city) - 21.4 mpg. I see similar (but different a different ratio) in the 2015 Hyundai Elantra while the 2008 Neon has similar ratios to the Altima.
I run 100% gas in all of my small engines and have for years to keep from having to put a new carb on them every year.

Way OT: Sales guy tells me to NOT run premo gas in small engine?

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