Saturday, July 26, 2008

CEL turned off itself

I was successful in getting the CEL to turn off by itself. Gassed up with the tank at ~32% ethanol, and within a few drive cycles, it was off. I had a long run up to O'Hare (about 50 miles each way for me) and that did the trick.

This is yet another confirmation that 30% is a safe limit for the amount of ethanol this car can run without fear of a CEL.


zenbeer said...

Ok, so I burned off my first custom blend of gas and ethanol which was a rated E23 (23% ethanol to 77% regular unleaded) and I re-filled my car today as I drove in on vapors to the Conoco.

MPG realized past 2 tanks (note, my 1998 SAAB 900-S is listed at 28mpg/hwy 21mpg/city). This last tank was approximately 80% city driving and 20% highway.

Miles per gallon realized (E23): 19.8mpg
Previous tank (E10) miles per gallon: 21.5mpg

Cost per mile (E23) Miles per dollar
$0.157 6.387

Cost per mile (E10) Miles per dollar
$0.176 5.673

I refilled the tank today:

5.01 Gallons E-85 @ $3.099/gallon
11.88 Gallons E-10 (regular unleaded) @ 3.789/gallon
$60.50 fill-up costs
New ethanol blend: 32.2% or E32

It is important to note, that it has been about 3 weeks since I filled up, E-85 remained at $3.099 the entire 3 weeks AFAIK with little, if any, price fluctuation here. My mpg drop was minimal for local driving. I want to try an E40 tank on mostly highway miles next for a trip to Springfield, Mo. and back to see the results before Labor Day.

Results of the E32 tank will be posted when it's burned through.


Anonymous said...

2.0T boi here. Can you make your spreadsheets available? I'm trying to figure out if it's worth it to cross a $6.00(!) toll bridge to get to the only e85 station in New England.

buzzcut said...

I'm not entirely sure how to post a file in a blog.

I was thinking about writing a widget that does what my spreadsheet does, and reports what the price of E85 should be. Unfortunately, this is slightly more trouble for me than writing a spreadsheet, as I don't know Java or anything like that.

buzzcut said...

MPG, go a little slower on your E85 increase. If you look back on my posts, I got a CEL when I went from 30% to 40% on one fillup. Yet when I gradually increased the E85 by half a gallon per tank, I was able to get damn near 40% without a CEL.

This, of course, takes a lot longer to get to impressive sounding % of ethanol in your tank. But I really think that it's the only way to get the ECU "used to" the ethanol.

buzzcut said...

Check out They have a widget that tells you if it is worth it to fill up with E85 or not (and they tell you what the price for it is in your area).

Basically, if it is 15% less than gasoline, it's worth it. Just take the toll amount, divide it by the number of gallons in your tank, and add that to the price of E85. If it is still 15% less than gasoline, it is worth it (you might also want to add a estimate for what your time is worth, as well as add a mileage penalty. The IRS allows you 50 cents a mile these days, use that to calculate the extra cost of the extra miles to the E85 station.)

Anonymous said...

Well, I got to the only e85 station in New England last week without crossing the Tobin Bridge and filled up with 5/8 of a tank of e85. This was the highest concentration of ethanol I had put in the tank to date. No problems at all. I burned through more than 5/8 of that tank (~25 MPG) on the ride home and to my work location the next day.

Remember how I said you had inspired me to ruin my car? Well, I stumbled upon another e85 station and topped off the tank with no gasoline just to see what would happen, I guess. About 15 miles from the station, the CEL went off. I burned a quarter of that tank (19 MPG, mostly highway -- terrible) before topping it off with regular unleaded. The light went dim after about 100 miles.

Again, I'm not keeping rigorous notes, but I my observation is that I can run okay with as little as a quarter of a tank of gasoline. Even so, I don't think I'll push it like that again -- I'll only use e85 in half tanks from now on.