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Old 12-10-2003, 09:26 PM
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Join Date: Dec 2003
Posts: 162
1989 300te...what octane?

My mechanic, who just did a new head on my 1989 300te says to use this ok?
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Old 12-10-2003, 09:38 PM
haasman's Avatar
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Join Date: Jun 2001
Location: San Francisco, CA
Posts: 3,096
Your car techically calls for premium fuel. If your head had to be shaved the compression will also rise as a result, thus even more reason to use premium fuel.

This topic has been discussed many times, with many pros and cons.

Some buy mid-grade fuel of good quality.

Whatever you do, be sure to keep a window open under acceleration and listen for pinging. The tell tale sign of pre-ignition.

I have found that after using mid-grades etc, the cars all run better with premium.

'03 E320 Wagon-Sold
'95 E320 Wagon-Went to Ex
'93 190E 2.6-Wrecked
'91 300E-Went to Ex
'65 911 Coupe (#302580)
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Old 12-11-2003, 12:18 PM
pesuazo's Avatar
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Join Date: Oct 2002
Location: Near Raleigh, NC
Posts: 580

Agree with Haasman 100%.
The head in my car was done years ago, compression due to shaving at around 200 psi on all cylinders. Bad idea to use 87 octane at that compression. Can probably run Diesel
Do a compression test, and take it from there.
1999 Porsche 996 Carrera Convertible
1994 420E - SOLD
1986 300E - SOLD, what a car
609 Certified
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Old 12-11-2003, 10:05 PM
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Join Date: Aug 2001
Location: Evansville, Indiana
Posts: 8,150
Yeah, you CAN use 87 octane, but I'd not. Use 91 octane or better. You could use 80 octane if you didn't car how long it ran.....

I run all the gassers on 92 or 93 octane premium. They all run better on it, even the 280 SE pings on midgrade.

1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!
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Old 12-12-2003, 11:08 AM
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Join Date: May 2002
Location: Mass
Posts: 1,127
That motor has a relatively high compression ratio.
It is one of the few motors (in the general automotive world) that actually benefits from higher octane fuel.
I generally run mid-grade with good results, but I bet my compression [at 215k] is not as good as yours is after that head rebuild. If the head was shaved, compression could be even higher than when new. I would bite the bullet and go for the premium.
1986 300E 5-Speed 240k mi.
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