Best Fuel for 928 S Euro

[luthir2]

I was luck enough to get the higher hp 928 and have been using 93 octane unleaded. Is this the best choice? is there an additive I should be using?

Opinions are appreciated!

[stepson]

93 octane is the preferred choice for fuel for the higher compression Euro models.

Put your year model in your signature line so we will all know which year model and version you own.

I use a bottle of techroline with a full tank periodically to keep things in the fuel system on the up and up.

[Pete R]

Additives are mostly gimmicks. Techron is a great fuel system cleaner but it does something to your oil to damage it so change your oil after a treatment

[SMTCapeCod]

If you do the math, it is hard to justify consistent use of an additive.

The model year of your car bears on the answer to your question.

The earlier RoW/Euro cars had slightly higher compression. So tending to your ignition system and especially ignition timing is important, as is making sure you don't have vacuum leaks that could lean out the AFR.

Running premium fuel is definitely a good idea.
Techron is a decent cleaning agent, as is (and I hate to say it because it is a bandwagon brand but also works, Seafoam).

I haven't come across data about Techron or other cleaners having adverse affects on the crankcase oil-- I'd be interested in a reference or datapoint to substantiate that.

If you have a CIS mechanical injection car, bear in mind that the shellac and buildup that is 'cleaned' out of the fuel system upstream of the injectors, will enter the fuel flow and can cause occlusion/blockages at the various screens in the system- at the fuel distributor, warm up regulator, etc, or can cause the injectors to stick. So, cleaning agents can be a bad thing, even the ones that work....

[Pete R]

Originally Posted by SMTCapeCod

I haven't come across data about Techron or other cleaners having adverse affects on the crankcase oil-- I'd be interested in a reference or datapoint to substantiate that.

I haven't used it in well over 10 years but iirc the super concentrated version said it right on the bottle, and I was told about it at a Porsche tech day by the Porsche tech. This may no longer be the case.

[Danglerb]

Generally the lowest octane fuel that doesn't ping is best, but none of the Euro motors have knock or ping sensors, so a slightly conservative spark advance might be good.

Proper AFR in all cylinders is very important, which means a good matched set of cleaned injectors, and no intake air leaks.

[luthir2]

Thanks for all the advise! Sorry I left off that it is a 1980 euro s.

[stepson]

Originally Posted by SMTCapeCod

If you do the math, it is hard to justify consistent use of an additive.I generally agree with this statement, however with the advent and inclusion of corn syrup into our present day fuels, I believe it may be necessary to include something in the fuel to "melt" those deposits to minimize blockages

I haven't come across data about Techron or other cleaners having adverse affects on the crankcase oil-- I'd be interested in a reference or datapoint to substantiate that.As would I. I'm not saying it's not true, but I've never ever heard that and can't imagine that I would never have heard of the lawsuits that would have ensued had it been true.

If you have a CIS mechanical injection car, bear in mind that the shellac and buildup that is 'cleaned' out of the fuel system upstream of the injectors, will enter the fuel flow and can cause occlusion/blockages at the various screens in the system- at the fuel distributor, warm up regulator, etc, or can cause the injectors to stick. So, cleaning agents can be a bad thing, even the ones that work....

If the varnish/shellac were to dislodge in one piece, absolutely it would be bad for your fuel system and the performance of your engine. Using an additive that would "melt" the existing varnish/shellac and flush it through the combustion chambers with the burnable fuel would obviously be more optimal. If I have the choice between using a cleaning agent and dealing with deposits left from all the crap put into fuel, I'll use the cleaning agents.

My $.02