85 octane
#1
85 octane
Ive previously posted that my cars performance and mpg is the same on 85 or 91 octane (lowesr and highest in CO due to combustion in our elevation). Ive been going back and forth between both. However i saw a video on YT that stated if you premix, which i do, that you need to use hi test only. Any validity to that statement?
#3
good question... the octane rating refers to the resistance to pinging and detonation. the reason many run 91+ octane is because the high compression and rotary heat factor. being that premix is there to lube the seals thus creating LESS heat id reason it wouldnt matter which octane you use. but id be curious to see if theres something else im not thinking about? perhaps the premix has a "lower octane" persay, thus requiring 91. deffinatly looking forward to a responce from someone with more experience.
#4
Smoking turbo yay
good question... the octane rating refers to the resistance to pinging and detonation. the reason many run 91+ octane is because the high compression and rotary heat factor. being that premix is there to lube the seals thus creating LESS heat id reason it wouldnt matter which octane you use. but id be curious to see if theres something else im not thinking about? perhaps the premix has a "lower octane" persay, thus requiring 91. deffinatly looking forward to a responce from someone with more experience.
Given the rest of the engine designs, my theory is that the car is just tuned to run on 91 to squeeze out the most power from the engine.
Premix lowers the octane, but probably not by much if you go with the ~250:1 ratio recommended.
#5
fair enough. that makes me wonder though if 91 is recommended for the lower compressions rotarys that premixed? granted our engines stock have very poor heat managment even for rotary standards
Last edited by Zeox; 12-22-2018 at 06:10 PM. Reason: my grammer and typing skills suck
#6
Registered
iTrader: (1)
I don't think the heat reduction due to premix is noticeable or even measurable. That's not where heat comes from.
The octane reduction is similarly not a factor. Run what you want, especially in rarified air, if you're not pushing the car. If you race it, high octane is cheap insurance.
The octane reduction is similarly not a factor. Run what you want, especially in rarified air, if you're not pushing the car. If you race it, high octane is cheap insurance.
#11
Smoking turbo yay
Engine detonation means you can have fuel ignite before you properly ignite it with spark plugs. That's very bad for the engine.
Knock sensors are there to adjust the timing so it will ignite the air fuel a bit earlier in the compression cycle, but that reduces power.
Knock sensors are there to adjust the timing so it will ignite the air fuel a bit earlier in the compression cycle, but that reduces power.
#12
Engine detonation means you can have fuel ignite before you properly ignite it with spark plugs. That's very bad for the engine.
Knock sensors are there to adjust the timing so it will ignite the air fuel a bit earlier in the compression cycle, but that reduces power.
Knock sensors are there to adjust the timing so it will ignite the air fuel a bit earlier in the compression cycle, but that reduces power.
#14
Smoking turbo yay
Yep, there is a difference between the two, but I still confused them.
#15
Grand Chancellor
Since RX-7 NA days, I have ran low octane. My RX-8 is 13 years with 87 octane and dino oil diet. Did experiment with 91 since the manual called for it. But after a few months didn't feel any measurable differences and have switched back to 87. Vancouver, BC weather is fairly mild even in the summer. Original engine with occasional Italian tune-up. YMMV.
There are some good rotary literature that discusses gas requirements specific to normally aspirated rotaries. Suggest to read them up to get educated and make your decision.
There are some good rotary literature that discusses gas requirements specific to normally aspirated rotaries. Suggest to read them up to get educated and make your decision.
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