Macster

91 octane is unfortunately a bit less than the optimum 93 octane. But the engine will be fine.

The DME constantly adjusts the timing and fueling to meet the torque demands of the driver and keep the engine within its design limits.

Funny I was expecting 93 octane gasoline to be plentiful in OKC.

It does make a difference. I had a chance to run 93 octane gasoline in my Turbo on a road trip that had me going through Wyoming (among other states) and 93 was plentiful and inexpensive. The engine was markedly better with 93 octane gasoline. I'd run 93 all the time if I could but I wouldn't pay double nor drive across town for it.

A 10% blend of ethanol will be ok. I've run that stuff for over 100K miles in my Turbo and over 200K miles in my Boxster with no ill effects.

Just buy a top tier gasoline and from a busy station

Macster

That's to be expected and is my experience too. Loved nailing the throttle on I-80 in Wyoming at 7K feet above sea level (way above up to over 8K above sea level) and seeing a solid 0.8bar even a solid 0.9bar boost on occasion. The car ran like a scared rabbit even at altitude.

okiedude

I have a philosophical aversion to corn gas. Unfortunately that's all you can get in many parts of the country. We usually have the choice, at least. I understand E85 is a great power adder, but I prefer 110 leaded for my race car. I'm kind of old skool that way-LOL. Yea, it's weird that here in the heart of oil/gas country 93 is rare as hens teeth.

Macster

While ethanol in gasoline is driven more by politics than science and no one would be happier than I if ethanol laced gasoline went away entirely a good fresh tank of premium gasoline with nominally 10% ethanol added is not the end of the world for your car.

Leaded gasoline is ok I guess for race engines but be aware the lead when burned creates abrasives and this causes accelerated engine wear. Longer valve and piston/cylinder life in engines that run on strictly no lead gasoline is one benefit of no lead gasoline.

Of course you should never ever use leaded gasoline in your Porsche.

And some of the bat $#@! crazy Porsche Turbo engine modder's swear by E85 (and a few of the craziest even go for methanol) but the stock Porsche is not designed to run on E85 (or methanol).

okiedude

I only use leaded gas in my 500 WHP Subaru dedicated race car, and I put a splash in my 1962 Chrysler 300H, I think it makes it happy. I would never put it in any modern street car.
Not a fan of e85 at all, but the "tuner" community loves it.

Kevinmacd

Mac not so sure your statement on accelerated valve wear is evident with leaded fuels. When no lead came out, the valves were the weak point, and had to be made of different materials to allow for longevity while using no lead gas. Lead was always viewed as a octane booster and a lubricant for valves

bella1

I saw the same .6 until I installed Kevin's UMW flash which now reads 1.1. Big difference and well within the limits of these engines.

Macster

When unleaded gasoline was on its way there was some concern about valve seat wear but it proved to be overblown.

IIRC a test/study (by GM, which BTW was the originator of lead in gasoline but at the time the goal was to find a use for a waste metal not to preserve engine internals) of truck engines found some exhaust valve seat recession but the type of usage these truck engines received did not match up well at all with the usage passenger vehicle engines received and the valve seat recession proved to not be the issue. However, some sought a cure and one offered was to installed hardened exhaust seats but the "cure" proved to be worse than the disease as some who had hardened valve seats installed had these work loose with disastrous results.

Exhaust valves and their seats are already quite durable. They have to be. Under some operating conditions even with a passenger vehicle -- albeit one like a Porsche -- the exhaust valves can reach a dull red temperature. Even in plain old passenger vehicle engines, exhaust valves (and their seats) are impressive pieces of hardware.

Kevinmacd

Mac - have to disagree there is plenty of evidence showing valve seat recession and higher valve degradation, especially in marine engines, were a constant load is on the engine as opposed to an auto engine. In the 1970s automakers changed their metallurgy in their valves and heads, and in addition additional lubricating compounds were added( phosphorous and sodium) to the gasoline. So if what you state is true than I would suspect that neither the auto industry or gasoline additives would never had been performed