Regular Unleaded or Premium?

[dspecorel]

A guy recently told me I should be using premium in my 76 280.

Is that true? (I hope not! $$$)

[Adenauer]

Owner's Manual doesn't lie. Calls for premium.

I'd venture a guess that the vast majority of folks run the cheapest fill they can manage. Short term use, you're okay. As a matter of course, I pump the high test. I figure it's what it calls for and if I cannot afford to run a car that requires it then I need to be looking at alternative methods of transpo.

[dspecorel]

Thanks for the info.
Not the answer I was looking for, but what the heck.
Looks like I'll be budgeting a bit more for gas from now on!
Don't tell the wife...

[Adenauer]

Bear in mind too, that premium back in the day would have been an octane value considerably higher than what we've got at the pump today.

When I can really afford it, I stop by Boeing Field and fill the tank with 110 low-lead AVGAS.

[Todd Miller]

I'll offer a slightly different opinion, but first agree that premium is what to use.

You can use regular (87RON) in it, as long as you've got the ignition timing dialed in to the point that the engine doesn't "ping" under the load of acceleration. This means you'd have to retard the ignition timing slightly.

Typically, an efficient way to do this is to find a hill in a neighborhood or city street and attempt to climb it at a low speed while having the engine in too high of a gear. For example: you start to climb the hill at about 30mph, shift into 3rd and then floor it. If you hear pinging (pre-ignition) under this load situation, you know the ignition is too advanced. Dial it back in small increments just until you find the point at which the engine no longer pings. That's the optimum advance you can run, given the compression ratio of the engine and the quality of fuel you're burning.

At this point, you can safely run Regular Fuel without damage.

I prefer to put premium in because they idle nicer and run better.

[JimFreeh]

The euro M110, when injected, produced 185hp.

The US fed version had considerably less hp, and I understood a lot of this was due to lower compression. If that is indeed the case, then the US version may be ok on regular gas......

Don't know for sure, never wanted a US engine, but I own a euro and have had another previously.

Also, octane ratings have changed in how they were measured. We now use MON+RON/2 to arrive at the 87-91 spread, whereas we used to use only one component years ago, which typically gave an octane rating up to 100. Or more, if you used Sunoco....

Jim

[Wodnek]

If you retard the timing on an engine you lose fuel efficiency, probably more than the price increase of premium. Now that fuel is over $3.00 a gallon the extra 20 cents for premium is only about 8%.

[tivoklr]

ok, since I'm sitting at the beach reading this thread, and don't have access to my owners manual, should I be running premium in my 1970 280S (dual zeniths, straight six).

Add to the mix that this car lives at 8000 ft.

Thanks for the insight.

[Wodnek]

Originally Posted by tivoklr

ok, since I'm sitting at the beach reading this thread, and don't have access to my owners manual, should I be running premium in my 1970 280S (dual zeniths, straight six).

Add to the mix that this car lives at 8000 ft.

Thanks for the insight.

I know little about the older ones, but at 8000 feet octane requirements drop. I would think midgrade fuel would be sufficient.

[280EZRider]

The US 110 is most definitely a low compression engine 8:1 with flat pistons. The Euro 110 is high compression with 10:1 with domed pistons. I have been runing my 280E US 110 engine on regular unleaded for about 7 years now with no pinging and retarding of spark.

[PanzerSD]

My M117 loves premium, runs like crap on regular I agree with the smoother idle comments, and it's only 4 cents more than regular @ 1.02/L it's a 90$ fillup, which hurts my wallet a bit but the increased idle and overall drivability is worth it, and this is with questionable camshafts..

[fj bertrand]

I have a euro m110 in my 280sl. I use only high test. When I run autocross I have a jug of racing leaded fuel 110 octane (2.5 gal) I dump into a nearly empty tank. I think it helps performance...