redwagon02
Member
- :
- '08 F150 FX2 screw - '06 G35 coupe - '06 GSXR600
The cheapest sh!t I can find. No money for gas anymore.
What octane do you use?
- Thread starter FLSilverP5
- Start date
FLSilverP5
Member
- :
- 2002 Protege 5
LOL what are you guys like 2? Trust me there are tons of P5's out there that can kick the crap outta ur MSP. And yes the thread was for P5's cuz that's what i have. I know mazda suggests higher then 87 for MSP thats why i didnt ask for it. I wanted to get a comparision of the same cars that u r suposed to put 87 octane gas in.
Don't our cars in particular run especially rich in the first place? makes it seem all but silly to me to push ANYHTING higher than the lowest octane. I've actually done some extended testing with this. Using Chevron 87 vs 92 trying to prove a point to a friend about fuel economy. 5 tanks of each, and i actually alternated some as well. Environmental and driving conditions were pretty set between everything and most involved driving up the pass to go boarding as that's when I put alot of miles on my car. I averaged 28.6mpg on 92 and 29.3 on 87. Not that this is the most scientific test, and my friend only had like .5mpg difference himself, but I'm prett convinced it makes a mileage difference. as far as anything else. Higher octane is prettymuch worthless unless you're heavily modded, and even at that alot of ppl overestimate what they've REALLY done, basically if you ever hear your car knock, up your octane..
Anyone notice the diff in octane ratings in different elevations? I noticed awhile back when I drove to Colorado octane was much lower. Also interesting to note. but mid-grade is essentially just a mix of the 2 (ever notice how fuel trucks only have 2 diff tanks on them?) I can't remember the exacts, but it's a bit less higher octane than low, A friend's dad used to own a gas station, and I ran the numbers once. It's actually cheaper to buy A couple gallons of high grade on top of some low octane.
As far as the whole issue of it being bad to switch, I don't KNOW for sure, but it seems to me that basically your ECU gets "used" to one sort of gas, so it essentially doesn't take full advantage of another one when switching unless you re-set your ecu by disconnecting your batt for 15min and pumping your brake pedal to release any residual juice....
Anyone notice the diff in octane ratings in different elevations? I noticed awhile back when I drove to Colorado octane was much lower. Also interesting to note. but mid-grade is essentially just a mix of the 2 (ever notice how fuel trucks only have 2 diff tanks on them?) I can't remember the exacts, but it's a bit less higher octane than low, A friend's dad used to own a gas station, and I ran the numbers once. It's actually cheaper to buy A couple gallons of high grade on top of some low octane.
As far as the whole issue of it being bad to switch, I don't KNOW for sure, but it seems to me that basically your ECU gets "used" to one sort of gas, so it essentially doesn't take full advantage of another one when switching unless you re-set your ecu by disconnecting your batt for 15min and pumping your brake pedal to release any residual juice....
Last edited:
FLSilverP5
Member
- :
- 2002 Protege 5
isnt it bad to change the octane u use?
Poseur said:
Yes, that's true. I just moved from Salt Lake City and lived on the bences of the wasatch mountains (elev around 5,000 or so), and it was common to see 84-85 Octane as a standard back there. I forget the scientific reasoning behind it, but it has something to do with the elevation alright. Problem comes if you ever have to leave the area and drop down back around sea level (like I did), so I always stuck with 87 or 89 Octane no matter what.
My dad hated it, as his Miata's take very high octane (91 I think), and that was a premium in the higher elevations.
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- protege5 2002
so a lot of people used 87 if their mp5 is stock. . . hmm i used 91.
i guess i wasted money. =(
i guess i wasted money. =(
i use 93 to combat knock/detonation. sometimes its hard to find over 91 and believe it or not it makes a difference. if you cant find 93 or higher and the place has a higher elevation (like CO or some parts of AZ) you might as well turn down the boost to about 6ish, whereas im running 8 now. in CA i heard 93+ octane is almost non-existant.Poseur said:
There's a lot of confusion about octane. I actually took a mechanical engineering class on internal combustion engines in college. Here's what I remember:
Octane is solely a measure of how succeptible the fuel is to pre-ignition (knock), which is the fuel-air mixture igniting before the spark. Higher octane is higher resistance to knocking. (R+M)/2 is the 2 methods of calculating octane averaged together (lab method & test engine method).
Octane has nothing to do with the btu content of a fuel. Different grades might have different heat content, but I'd need a Chem-E from a refinery to tell me for sure.
Tetre-ethyl lead ( in "leaded" gas) was an additive to reduce knock & increase octane. In the early days, premium gas was the regular with a spoonful of TEL added from a jar. This had to stop when they figured out that the highly-toxic stuff was killing the pump-jockeys.
A small amount of knock is actually beneficial to combustion. It mixes up the mixture & helps with complete combustion. High levels of knock stress the pistons, etc. This is why if your car doesn't knock, don't put premium in it. The exception is if your car has a knock sensor, which will advance your timing until the car starts to knock, giving you the most power you can get. In this case, a higher octane gas should help performance. If you move a knock sensor to the firewall, I would assume that the timing would then advance to the maximum position, & that you're in danger of reducing your engine to scrap.
Lots of mods contribute to knock. Spark-ignition engines are typically limited in power by the amount of air you can get into the cylinder. More air means more compression, means more heat. Anything that heats up the fuel-air mixture makes it more likely to knock: turbos/superchargers, stroking, domed pistons, etc. Anyone remember water injection? It cools the mixture to prevent knock. Most stock engines that get factory turbos have the compression reduced - to prevent knock, which is why lots of turbos stink at low rpm. (different topic, but nitrous gives you raw oxygen which keeps you from having to pull it in thru the intake)
One thing you might get with premium is more additives. I know for a fact that the "Techroline" thing in Chevron gas comes in cans that the fuel truck driver adds in the field.
Hope this helps.
Scott in ATL
Octane is solely a measure of how succeptible the fuel is to pre-ignition (knock), which is the fuel-air mixture igniting before the spark. Higher octane is higher resistance to knocking. (R+M)/2 is the 2 methods of calculating octane averaged together (lab method & test engine method).
Octane has nothing to do with the btu content of a fuel. Different grades might have different heat content, but I'd need a Chem-E from a refinery to tell me for sure.
Tetre-ethyl lead ( in "leaded" gas) was an additive to reduce knock & increase octane. In the early days, premium gas was the regular with a spoonful of TEL added from a jar. This had to stop when they figured out that the highly-toxic stuff was killing the pump-jockeys.
A small amount of knock is actually beneficial to combustion. It mixes up the mixture & helps with complete combustion. High levels of knock stress the pistons, etc. This is why if your car doesn't knock, don't put premium in it. The exception is if your car has a knock sensor, which will advance your timing until the car starts to knock, giving you the most power you can get. In this case, a higher octane gas should help performance. If you move a knock sensor to the firewall, I would assume that the timing would then advance to the maximum position, & that you're in danger of reducing your engine to scrap.
Lots of mods contribute to knock. Spark-ignition engines are typically limited in power by the amount of air you can get into the cylinder. More air means more compression, means more heat. Anything that heats up the fuel-air mixture makes it more likely to knock: turbos/superchargers, stroking, domed pistons, etc. Anyone remember water injection? It cools the mixture to prevent knock. Most stock engines that get factory turbos have the compression reduced - to prevent knock, which is why lots of turbos stink at low rpm. (different topic, but nitrous gives you raw oxygen which keeps you from having to pull it in thru the intake)
One thing you might get with premium is more additives. I know for a fact that the "Techroline" thing in Chevron gas comes in cans that the fuel truck driver adds in the field.
Hope this helps.
Scott in ATL
