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! I'll also post in the technical forum.

__________________

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.

add a bottle of octane-booster.... I doubt you will have any sort of damage done.

Thanks, guys!

I'll just lay off the throttle for a while and fill up with premium when half empty as suggested.

No one else need post unless there's something more I really need to do.

THANKS AGAIN!

__________________

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.

If your M104 has a knock sensor, you should be okay. I remember hearing somewhere that it does? I could be wrong.

You will be okay as long as you aren't hearing audible detonation.

-Sam