Part time E85 and OCI
 

I run E85 in the summer and E10 91 octane in the winter. I read that if running straight E85, you want to cut your oil change interval (OCI) in half, which would be 3750mi. I did my last oil change with 5000mi on the oil, probably a 60/40 ratio of E85/E10. My oil analysis came back great, with a suggested interval of 7000mi. That almost the same as the factory recommended 7500mi with no E85! Of course there are a million variables involved in a achieving a proper OCI, and I guess the numbers don't lie.

Anyone else running E85 or part time E85, and what is your OCI?

That sounds about right. With synthetic oil you can safely exceed the oem oil change interval anyways. Im on eneos sustina and im changing every 10k with approx 50/50(e85 and 91). I havent done a UOA though, so I have no idea what condition the oil is in after each change.

Thanks for sharing, I've been wondering if it is really necessary to cut oil change interval in half or not.

I also know some local 86's that have done 7-8,000mi on solely e85 on stock oil and told their analysis was fine.

I'm currently on E85 since my last oil change about 3k miles. Could you tell me where you sent the oil analysis? I'm thinking to get it done as well.

Also, is there any other factors that we are able to check to determine if this increased oil change interval is just a myth?

As long as your oil is E85 compatable , generally most SN or GF5 rated oils are you should be fine its always best to check in the manufacturers spec to confirm.

some cars generally FI depending on tune boost levels ect may get some fuel dilution with E85. or some people just like to be cautious especially if tracking or driving hard in adverse or hot conditions. If you oil ananysis comes back fine then you can likely run the normal oil change intervals.

However some people like to change more frequently even if not running e85, its just personal preference,, go off the oil analysis.

I had my oil analysis done at Blackstone Laboratories. I've read that E85 can cause higher than normal levels of fuel dilution in the oil, but not sure how to check that other than to do the oil analysis.

I've run primarily E85 and I've done changes at 3k miles and at 7k miles, all had considerable fuel wash and smelled strongly of ethanol. I haven't sent any oil samples for analysis, so it's purely anecdotal, but I change every 3k miles now because of that. My car gets beat the hell out of, and I enjoy fiddling with the car, so I don't mind the frequent oil changes. Whether it's necessary or not though, I can't answer that.

Update / Thread Ressurection:

I sent in my oil for analysis after 7K miles, again with about a 60/40 ratio of E85/E10. The analysis came back great, no sign of fuel dilution or abnormal wear. It was suggested that I try 9K miles next time, but I think I'll just stick to the stock inverval of 7.5K miles.