[I did read the fine thread a few lines down that's similar to this. I guess I really just need to know if the engine will be okay. It's a '95 E-320 with the 104 engine.]

After working a twelve hour day and then going to the gym, I was too tired to realize that I filled the tank of my E-320 almost all the way up with mid-grade gasoline. (This station had the premium in the middle and the mid-grade on the right, DUH!) I then topped it off with a few gallons of high-test.

I'd say the ratio in the tank now is 75% mid-grade and 25% premium.

Is there any cause for concern? Should I have the tank drained? If not, should I drive in a certain way to prevent any damage?

Thanks for any help!

__________________

Current:
2014 VW Tiguan SEL 4Motion 43,000 miles.

2016 Hyundai Santa Fe Sport (wife's).

Past:
2006 Jetta TDI 135,970 miles. Sold Nov. '13.
1995 E-320 Special Edition. 220,200 miles. Sold Sept. '07.
1987 190-E 16 valve. 153,000 miles. Sold Feb. '06.
1980 300-D 225,000 miles. Donated to the National Kidney Foundation.
1980 240-D manual, 297,500 miles. Totaled by inattentive driver.

Dear sfloriII:


There's nothing to worry about. Your car definitely has a knock sensor which automatically adjusts the firing timing. NO damage will be done.


Eric

Ditto. You can go down to 87 octane and still be okay.

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95 E320 Cabriolet, 159K

You are okay.

If you haven't attempted that performance tip where you can reset your timing over what was set at the factory (based on the use of lesser-grade octanes), there will be no harm done.

Plus, I find that when I'm stuck in a rural area for an extended period, sometimes I can't get much better than 87 or so...and I'm NOT puttin in that "gasahol" or whatever them "corn-squeezins" mixture is!

__________________
2009 ML350 (106K) - Family vehicle
2001 CLK430 Cabriolet (80K) - Wife's car
2005 BMW 645CI (138K) - My daily driver
2016 Mustang (32K) - Daughter's car