And you need to understand the concepts behind what you are discussing before commenting. "Them new German computers" you heard about do have limits and were not designed for cont. use of low grade and/or quality fuel. Kwiktsi did a nice job of explaining the rest.

 

If in doubt, spend the extra 2 bucks and fill up with premium. I really want my engine to last a long time. If it costs me an extra 2 bucks a week, then it's worth the money.
That's just half a grande latte for you Starbucks people.

 

Wait no more! I have been using regular 87 octane since my first fill up April 2004; have over 23,000 kilometers (approx 15,000 miles) and have never heard any pinging / detonation. Car has been completely problem free and never been back to dealer for service.

BTW, on our recent trip to Florida in April, I was getting over 30 miles per U.S. gallon consistently on the highway (average 5 - 10 miles over speed limit driving).

The only mods I have made is, full dual exhaust and free flow air intake. Needless to say, I would not take the risk of aftermarket 'performance' re-chipping.

I don't believe that premium gas is required despite what the manufacturer recommends. They would invalidate the exhaust but for what reason; the engine runs much more efficiently.

 

Much obliged...need to test it some more, but besides the couples cents per gallon savings, so far I'm averaging 7 mpg extra on the highway fuel economy...if that holds up in the city, I'd be saving mondo bucks, and my only gripe with the car since I got it (besides perhaps no coffee holders) was that the fuel economy was 18.5 MPG, way below what I was expecting...

I just hit 15K miles myself.
Glad to hear your car didn't explode!

 

No way! These are probably the same people who debate between milk causing cancer and probably think Tom Cruise is normal. I can appreciate you wanting to save money on fuel, but if so, drop the sports car and get a hybrid.

 

Well, I haven't heard ANYONE debating milk causing cancer and I certainly haven't heard anyone say Tom Cruise is normal. But, "drop the sportster and get a hybrid"? Rather narrow minded comment. As long as you didn't pay for it I say "run what you want. It's your car". Besides, running 87 octane will only cause the computer to slightly retard the timing, resulting in a insignificant, if not noticeable, loss of acceleration. Still fast enough to get you to traffic court on time.

 

I agree performance wouldn't suffer a noticeable difference, but for 10-15 cents a gallon, I'd rather be safe than sorry.

 

It's not only Utah, try Idaho, Wyoming, and Montana to name a few.

 

Running lower octane gas will leave higher amounts of carbon in your engine. I found that out the hard way on my 96 Chevy pickup after running 85 octane for four years and averaging about one O2 sensor every 18 months. The dealership scoped the head and recommended pulling them and cleaning them I chose option 2 go with a diesel Dodge Ram 2500 and I haven't been sorry since. Now let's talk about fuel prices with diesel at $.30 over premium.

 

I may put lower octane in as an experiment and check my mileage. Then I'll try it with some 102 octane booster and try it... then I'll compare it to my 91 octane MPG numbers.

Man... I really wish there was a linked roller AWD dyno near me...

Then I could REALLY tell you what the differences were...

 

I always run the cheapest gas I can in my crossfire. haven't a single problem yet. Though there is a slight noticeable loss in power when dropping from premium to low grade. I just let the computer handle the timing adjustment.

I haven't had time to research how the XF heads flow coolant, but most cars these days are reverse flow, thus cooling the heads before the block, and allowing you to run higher compression engines on cheap gas.
I know the 1990 - '95 LT1 Impallas and old Police cars had 10:1 compression ratio. And they used nothing but the cheapest gas possible in those squad cars.

 

Quote from DC dealer after purchase, "If you leasing use regular but if you own it and plan to keep it use premium".

The thing is that you don't hear detonation until the knock sensor has reached it maximum range of possible correction. The engine is detonation on regular, computer back up the timing, adds more fuel, it operating within the range and you don't hear a thing. Over the long term the crown of the pistons will develop small pin holes from the detonation. You are also more likely to develop deposit/carbon build up in the combustion chamber on regular (less additives). Those two things will create even more hotspots and it will slowly gets worse over time then you will start to hear detonation. The end will not be too far behind. I have taken many engines apart and have seen what detonation will do to pistons.

IMO like the dealer said if you plan to keep it, do your engine a favor, and use premium. Its the long term effect of using regular that's going to hurt.

Like the famous quote about changing your oil "Pay me know or pay me later"...

 

I've been running 87 in it since I bought it, no knocks (not even on startup or under hard acceleration). Mind you, I have just over 3k on it, but those would be the times when the engine WOULD knock. There is really no reason for those of us with the base or limited models to run 93 or 94, unless you want to squeeze every little bit out of the engine. Now those of you with the SRT-6 should run the highest octane you can get your hands on. Anything that runs compressed intake air needs the slower detonation the octane provides due to the enhanced compression. If you have any type of boost, the fuel-air mixture will ignite too quickly and will absolutely damage the engine over time, and your performance will be noticeable different (I used to drive a turbo back in the day, couldn't get out of its own way on anything less than 93). For the normally aspirated engines, 87 is fine as long as it doesn't ping. Carbon? Run some BG through it every once in a while, or fill up with premium on occasion. Most gasoline's now have soooo much detergent in them, carbon isn't really a problem.

 

I too run 87 and haven't noticed a demonstrative change in performance from 91. As an engineer, I can tell you the difference between 87 and 91 is minimal (if I remember from school correctly) and I'm sure that someone on this board is a chemical engineer and can explain the octane difference to all of us. I do notice that a lot of people on this board are very sure of themselves on the subject of 87 being dangerous to run, without anything to back up their statements... anything that qualifies as scientific that is. This is not the first time I've read an article stating that 87 is safe to run, and so I do.
Since I too don't have any scientific evidence to back up my supposition, I can only use my experience in 20K miles and say that I get 26-28 mpg consistently with 87 and more then acceptable performance. I would imagine that if you are driving your car hard a higher octane would be advisable, but something higher then 91. The old guys can remember when you could by 103+ and there is a difference when you’re talking that delta.
Just my opinion and experience...

 

This $0.02 being offered from someone who has Cocaine use as there Aviator. I would value that opinion based on those values shown.

 

Since this was originally my thread, I can report that in the past year w/ regular, noticed no appreciable difference in the X-Fire...every other car still drives like a turtle, and I have about the same fuel economy. I will note that I do have a lease, in response to some other comments.

Mike

 

OK, Octane and heptanes make up the 2 major components of gasoline, 87 = 87 parts Octane and 13 parts Heptane and so forth. The Heptane component provides combustion, but can easily ignite under compression, so cars with lower compression can use a mixture such as 87, but cars with high compression need 90 plus. If you are running a modern vehicle with a high compression engine and computer based ignition system, it will retard the timing to reduce knock, which in turn is basically reducing compression and finally reduced horsepower, this is a fact. How much power? I don't know but if you put it on a dyno you would see.

Airplane fuels still contain lead, so they put in an additive called TEL so this is a different rating system just in case someone ask why AVF is higher than 100.

 

Just incase anyone asks, I am an Electrical Engineer, but I own my own manufacturing business and most of what we sell goes into the Petro Chemical industry, so I hang out at refineries a lot.

 

I baby my car but I don't feel it was pointless to buy it because of how I treat my car. I think "babying" a nice car helps keep it in good shape for years down the road.

I babied my Miata and it was in beautiful shape for 17 years before I sold it in July. I credit it's great condition to consistent maintenance and driving her carefully. Nary a ding or dent because I was careful and I drive defensively as much as I can.

I am doing the same with my Crossfire. I want her to be in good shape for a long as possible. Point of buying it? Because I love it.

 

Talked to the service forman at the local MB dealership. He said the 3.2 engine would not be effected by using 87 octane. I have been using for 6 months and all is ok.

San Diego, Bob