mechanics I've talked to say it would just affect long-term reliability but is there really anything wrong with putting 87 instead of 91 or above octane in say, a BMW or lexus?
is there really anything wrong with putting regular unleaded in a premium unleaded car?
- Thread starter FAS284
- Start date
yes.
this will cause detonation (fuel ignites in combustion chamber spontaneously), and will eventually burn a hole in the top of your pistons.
this will cause detonation (fuel ignites in combustion chamber spontaneously), and will eventually burn a hole in the top of your pistons.
DivideBYZero
Lifer
- May 18, 2001
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If the car is modern, the ECU will compensate and it will not affect long term reliability.
If the car is pure engine, you will destroy your engine very, very quickly.
If the car is pure engine, you will destroy your engine very, very quickly.
DivideBYZero
Lifer
- May 18, 2001
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Not always true. Maps can only compensate so far in high performance setups.
Only cars like the M3 with it's per cylinder knock sensors and 25MIPS ECU can really cope with wide variance in fule grades. Most create an average for the fuel grade used over time.
Vic
Elite Member
- Jun 12, 2001
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Except if the car has forced induction, and then no modern ECU can prevent all detonation, and so reliability is still threatened.
I don't understand why people put regular in their premium-only cars when gas prices go up. Relatively speaking, premium becomes a better buy, not a worse one, when prices go up, because the spread in price remains roughly constant.
That may have been true 40 years ago but today there are conditionals that must be considerred to make such a blanket statement. If you are driving an old high compression vehicle with a carburetor and no electronic controls then running a lower octane fuel can definitely lead to detonation and damage the engine.
Now this simply is NOT true for most computer controlled cars with fuel injection because almost all have knock sensors that monitor detonation and retard the timing enough to prevent it. You do lose power when this happens but you are not going to damage the engine. You can also lose gas mileage. I tested my Taurus SHO with both regular and premium. With premium it had more power and got better mileage....enough so that by my calculations it was only costing me about $.05 extra to use the premium and the car performed better so it was worth it to me. My friend tested this on his car and he claimed his car required premium but ran fine and got better mileage on regular. Each car can be different and testing is required. If you hear audible "pinging" then you ARE damaging your engine.
My father drove the SHO the first 105K miles of it's life putting only regular gas in it even though it required premium from the manufacturer. I only put regular in it until during the summer months I started getting some "pinging" during shifting and then started using premium. After the testing I decided to only use premium. The car now has 220K miles on it and runs fine and has never had any engine work needed all the while running regular for far more than half those miles. You take from this what you want as I am just throwing it out there as a real world example.
If it saves you money and you don't take a hit on gas mileage and you don't drive the car to it's performance limits anyway it can definitely make sense. In my example it only cost me an extra $.05 a gallon or $.80 a tankful to enjoy the full performance of my vehicle so it was not a big deal. It will definitley be car and person dependent so testing is in order. For a time I ran regular in the colder months and premium in the warmer months because as the mileage on the car rose the extra carbon deposits on the pistons made the car detonate to a degree at times and it became outside the range the ECU could compensate for. Newer cars should be more tolerant. Each case will be different and you should determine for yourself what is best.
DivideBYZero
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DivideBYZero
Lifer
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NaOH
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I did read that. But my point is, it isn't even significantly more expensive either way. If your car was designed to run premium then why run your car with regular? There are tons of other areas to save money in. You don't know how much the long run costs will be.
- Oct 10, 1999
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With modern cars, it's generally fine. My dealer has on occasion even recommended putting in the cheaper stuff due to additives that many gas cos put in for winter conditions.
The only real problem is that it reduces your performance a bit. I don't imagine it's really an economical advantage to pump the cheaper stuff, but it certainly is not harmful to most modern cars.
The only real problem is that it reduces your performance a bit. I don't imagine it's really an economical advantage to pump the cheaper stuff, but it certainly is not harmful to most modern cars.
Originally posted by: Iron Woode
5.0L mustangs and my 5.0L Crown Vic don't have knock sensors.
No they don't but their compression is low enough that with proper tuning you can make them run on the cheaper gas if you don't go around racing all the time. If you have put on aftermarket aluminum heads it is even easier.
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