Hi guys I'm not new here but it's been a while. I have a 1995 springer softail it has the stock motor in it with an Andrews EV 46 cam, python pipes and K&N air filter.

My question for you guys is what octane fuel do you run in your basically stock motors like this ? here we have 87, 89 and 91 octane to choose from. I've always run the highest octane choice in my springer because I was led to believe that they had less (or no) ethanol in them and have heard that Evo's hate corn fuel.

I've always heard that running a fuel with more octane in a lower compression engine wasn't bad for it, it wouldn't gain you any power or anything but it wasn't bad for it, Some recent reading made me wonder if it is actually bad to run higher grade fuels in low compression motors or if it in fact will cause them to run worse. also would this change situationally ? would a motor like mine be hurt by higher octane out on the flat prairie but benefit from it up in the western mountains ?

So any advice on what to run ? thanks

 

I run premium because when I ran regular the motor would diesel when I shut it off.

 

I too have been led to believe you have to run high octane fuel in a Harley. Actually I've been told in ALL motorcycles. However, in my Honda Rebel's manual, it states must have a minimal of 85 octane. In all 4 Harleys I have owned, I still run either 91 or 93 octane. I feel that the higher octane keeps pinging to a minimal. I have noticed higher octane burns a bit hotter in my motorcycles. Perhaps someone with better info might chime in.

 

I run the best I can get. I have ethanol around me so I'm usually replacing fuel hoses every 3 years. I've had to make sure the carb was built to handle it too. The good news is most rebuild kits are made to withstand ethanol, but that **** still will burn through some seals. Just rebuilt the 2 bbl on the car with a kit for ethanol.

 

My 93 owner's manual says it'll run on 87 octane, 10% ethanol max. IIRC the stock compression ratio is like 8-8.5.

That being said, I've always run either 91 or 93 octane. All the stations in MI are required to sell 10% ethanol mix. Only a few stations have 'pure gas'. I buy 5 gallons of it ($3.99 a gallon), and run that in my outboard and small engines.

Nothing against the farmers, but there are better uses for corn than making a political statement...

 

Compared to sugar cane which is almost as efficient as gas, corn based ethanol is awful. I remember motor trend saying the e85 cars would lose a few mpg because the higher ethanol content. What's ****ed up is the more corn used for ethanol, the higher the cost of corn based livestock feeds and other corn based goods.

 

AMA has been fighting the EPA 15% proposal. Most motorcycle, outboard, small engine manufactures void warranties if 15% ethanol mix gasoline is used. Guberment looking out for us again...

 

High octane won't hurt it and in the summer can help you. Since the tank is only five to six gallons, price difference is minimal.

I am running high compression so I have to run 91 or higher, but even when I was stock, I always ran 91 or higher on all the bikes I ever had.

 

I am under the impression that higher octane fuel is less volatile. What I mean to say is that it can compress more before detonation. High test is said to give a "slow burn" compared to lower octane. That is why you get slightly better fuel economy from it as well.
As far as ethanol is concerned, it sucks. My pickup will run e85 and it is a joke. Truck runs like crap and fuel economy is less than half of dino juice. Companies like Lucas make an ethanol treatment that I run in all of my 2 stroke engines and it does seem to help them run better. I've never tried this stuff in the Harleys but it may help if your concerned with ethanol.

 

Truth be known, is that EV-46 in that untouched stock engine, actually has less ccp than an OEM cam.
87 or 93 wouldn't make much difference in it's performance.
Put that compression at 10.0, to correctly support that cam, and then, 91-93 would be the ticket.
Scott