regular gas & s4... real-world performance impact?
10-07-2008, 09:54 AM
#1
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regular gas & s4... real-world performance impact?
First, I know that one should not buy an S4 if one is worried about gas mileage, but just in case one would be.... Has anyone tried using regular gas in a B6 S4? I don't think there is any mechanical damage risk. Can you actually feel the performance difference in normal, everyday driving? I'm thinking of an S4, but 'worried' about the gas mileage, and using regular gas can save about 8% on gas cost. Thanks.
10-07-2008, 10:31 AM
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If saving $4/fillup is your tipping point, then the S4 is not for you.
Tires, brakes, oil and general maintenance on the S4 are going to be quite a bit more than on an A4.
On the issue of performance, yes, you will see degraded performance when using lower octane. If you don't care about performance, then why bother getting the S4? These cars run an 11.0:1 compression ratio, so you better believe I'll be running at least 93 on every tank.
On the issue of performance, yes, you will see degraded performance when using lower octane. If you don't care about performance, then why bother getting the S4? These cars run an 11.0:1 compression ratio, so you better believe I'll be running at least 93 on every tank.
10-07-2008, 10:35 AM
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Why bother?
Let's say you drive 10,000 miles per year. If you average 16-17 mpg over that whole time you'll buy about 600 gallons of gas. Now choose an average cost of $3.75/gal for premium you'll spend $2250 per year in gas. Your savings of 8% is only $180 over the whole year.
You won't damage the car using regular fuel, but performance will be impacted. It's not worth it IMHO.
You won't damage the car using regular fuel, but performance will be impacted. It's not worth it IMHO.
10-07-2008, 10:47 AM
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The knock sensors will compensate, to a point...
and timing will be retarded, hurting performance. You'll be pushing the gas pedal harder to compensate, worsening MPG and probably netting zero savings.
Add to that the possibility of a bad tank of 87 octane, causing the ECU to max out its ability to compensate, and you *can* risk damage.
It's a stupid, stupid, stupid idea from any and every possible standpoint.
Do you think the "minimum 91 octane" sticker and warning in the handbook is just for kicks?
Add to that the possibility of a bad tank of 87 octane, causing the ECU to max out its ability to compensate, and you *can* risk damage.
It's a stupid, stupid, stupid idea from any and every possible standpoint.
Do you think the "minimum 91 octane" sticker and warning in the handbook is just for kicks?
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10-07-2008, 02:17 PM
#8
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HP loss and dont drive the thing north of 4k rpm
Unless you like to feel the knock sensors working over time. A long road trip with sustained high way speeds, dont have a major amount of extra weight in the car and no major mtns no biggie. In those cases you're using maybe 50/60hp tops. But in stop and go and heavy accel stick with 93 or the best you can find.
10-07-2008, 03:39 PM
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Your savings will be nil at best. You will lose money when you take it to the dealer
and you find carbon buildup, hard starts, failing knock sensors, etc. I see it all the time at the BMW dealer I work at. Even at training, BMW states in their manuals that using regular fuel will not save any money. The computer compensates for less power/heat in the cylinder by lengthening the injector pulse, wasting more fuel. We even have an octane test we can do through our scanners to test. Pretty crazy
10-07-2008, 03:45 PM
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I did scientific tests (more or less) with my V6 and V8 Audis and 93 octane saved money
you get enough extra mileage out of high octane over junktane that you come out slightly ahead.
IN the long run you save even more money with less carbon buildup and ring damage.
IN the long run you save even more money with less carbon buildup and ring damage.