Generator Gas Requirements - Weird?

[deagle]

So I've read over and over, if the engine calls for regular octane, putting premium in it does nothing.

I have a Craftsman generator that has never been started. It sits a lot. I have access to Ethanol-free 90 octane gas that I use in my lawnmowers, chainsaw, etc. I also store the bikes with it in Winter as it supposedly does not "go bad" or do the damage as fast as E10.

I wanted to use the ethanol free gas in the generator, but in bold print in the instructions is says "Regular 87 fuel only!".

Could running 90 octane cause damage?

Thanks,

Don.

 

[Fred W]

In a word: No.

 

[eflyguy]

Seconded - no!

 

[Viper Pilot]

Totally agree!!

 

[Fred W]

Alright, so we're all being a little too cute here, maybe.

My interpretation of the "warning" is that you should not use any regular gasoline below 87 octane.

"What's that" you say? Yes, it is true. In some parts of the country, especially those at higher altitude, they sell regular gasoline at less than 87 octane rating.

I believe the warning on your Generator engine is that you shouldn't use any gasoline below 87 octane (regardless of what grade they call it).

So if your regular is 87 where you live, you're good to go. But if you live somewhere that regular is only 85 octane, splurge on the mid grade or whatever puts you over the 87.

Sounds all simple now, doesn't it?

 

[Redfish Hunter]

Could you simplify that explanation?

I am going to hypothesize that there is enough variation in fuel quality, age, contamination, additives, and brands that the real life differences between an 87 octane gasoline and a 90 octane gasoline are negligible.

Even if it did cause some sort of damage, how many hours of running would that require? And how many hours a year does this generator actually run?

 

[Viper Pilot]

I think what the warning is actually saying is to not use anything like E85 or even E15. Many small engine mfgrs. are concerned that customers will try to fuel with blends having high alcohol content. My outboard engine and small generator engine owners manual have similar warnings.

 

[HotRodZilla]

What has already been said, but with a small disagreement with Fred. I wouldnt fill with the 85 octane sold in Colorado and then run something at sea level, but as the altitude gets higher, the lower octane levels drop. So long as you're at altitude, you shouldn't have any problems.

As a test, I once avoided the low octane fuels, which forced me to use 88 octane, because the regular was 85, mid was 88, and premium was 90. There was no difference in performance or mileage that I could tell. Performance is subjective, but the numbers don't lie.

My bet is you're good running the 90 in there. If you store it for long periods, I'd still stablize it.

 

[Fred W]

It's already NEPRT so we can talk about Octane here I guess.

Octane isn't about getting more performance. It's only about avoiding detonation. You don't miss the octane until the pinging starts. If that happens often or severely enough internal damage can result.

Using higher octane fuel doesn't give an engine more power, but it does allow you to advance the timing and / or compression enough to make more power without getting detonation. That is all it does.

The rare exception is with engines with variable timing and/or variable (effective) compression ratios from forced induction compressors (super or turbo charging). On those engines they can be fitted with sensors to allow increased power output to the point where pinging is first detected and then slightly backed off, dynamically. So running higher octane fuel in those specific engines will give you more power.

But the lawnmower in the OP is not likely supercharged, nor have variable timing, so that 90 octane isn't going to help a thing.

 

[danh600]

My two cents.

90 is fine for the generator. I would also add some stabil or sea foam.

Ethanol free is worth the trouble and expense on small engines. Ethanol is fine for your car, truck, even your modern motorcycle. You should be riding your FJR enough for the gas not to go bad.

However I am a firm believer in ethanol free 90 rec gas for small engines. Even living in Florida and running them most of the year I was having trouble with my lawn mower and weed eater. They would first become hard to start. Then not even run. I had the carbs cleaned and now only run rec 90. Been doing that for a couple of years. My lawn mower, pressure cleaner and weed eater still start in a max of one or two pulls.

I have to drive about 15 miles to get rec gas, but it's worth it. Well that and there is an awesome Taco Stand next to that gas station.

 

[lnewlf]

OP states that the generator has never been started....why not just drain the tank and run the carb dry...mine is seldom used and I don't have to sweat bad gas...

 

[Fred W]

Actually, that is what I do as well. When I'm done using it, after the power comes back on, I turn the gas petcock off and run it until it stalls. Then I drain the tank back into a gas can to be used in lawnmowers, snowblowers, whatever. That way the gas in the Jerry can is fairly fresh all the time

 

[BigOgre]

^^ Same here. Fog the cylinder also.

 

[eflyguy]

Seals and O-rings will dry, then split. That's why.

 

[Niehart]

Good gas [no corn], stabilizer of some sort and run under power once a quarter for 15 minutes.

I don't have one but I got damn tired of working on my neighbor's generator in the middle of a storm with rain running down the crack of my plumber butt.

So once every four months [yes I have a reminder on my laptop] I go start his generator.

We haven't had problems since I start doing this. And yes I do now have a good power cord that will reach from his home to mine.

 

[deagle]

Original poster here. I'll double check the exact wording. I "thought" it said "do not use premium fuel".....but maybe that was my interpretation. I will check this evening.

 

[Heen]

Fred is very correct on his middle post about octane being for pre-detonation of fuel allowing higher compression and advancing the timing. At higher altitude you have less air so the compression is less than at see level. For round numbers you loose about 4% for every 100 ft in elevation. So for example: If you had a 100 HP engine at sea level, when you get to 5000 ft. you will only have an 80 HP engine, and only require 85 octane.

I would use fuel stabilizer in my fuel over draining. If your generator has not run and has no gas in it, run the 87 octane but if it has been sitting a 6 months or more with fuel in it and no stabilizer, I would drain and clean the carburetor and especially the jets.

 

[Redfish Hunter]

The operator's manual for my Centurion generator clearly states to run the tank dry before storage. I ignored this and it is costing me money.

 

[yamafitter]

The issue with most small engines is ethanol is very hard on the diaphragm in the carburetor and other rubber components in the fuel delivery system that most small engines still use. Since the higher octane fuels mostly have less or no ethanol most manufacturers recommend using the higher octane fuel. As far a storage goes a rule of thumb goes is if your small engine has a metal fuel tank you want to store the engine with the fuel tank full to stop rust forming in the tank. Obviously if the tank is plastic this is not an issue.

The compression ratio on most of these engines is not that high. My Echo chainsaw is only 6.7:1 and my Honda 3000is generator is a little higher at 8.5:1. Neither one of these motors compression ratios are high enough to have pre-detonation issues due to octane rating of regular fuels which locally run in the 87 Octane range. My WR450F on the other hand is high compression, high rpm motor and requires the higher octane fuel to prevent pre-detonation.