Civic Vtec-E lean burn: Better burn on lower octane fuel?

[tim3058]

Yep, gauge shows its just about exactly 6" Hg to hold lean-burn. My car has had a real hard life, 55 tank mpg is downright incredible, not likely to occur on mine anytime soon. I filled up tonight, tank mpg was 49.00... a record for me, but not sure if 86 octane had anything to do with that, more likely trying P&G did it.

[oldman]

lean burns quicker and thus internal engine pressure is much higher. My thinking is sure ethanol has higher octane, this just lets big oil use less octane boosters in plain jane fuel. My HX lean burn lost about 15% or more when ethenol was introduced into Texas, the MPG loss is even greater with lower octane fuel. yes my car is in perfect shape, yes I keep pen and paper of every fill up. I've gone from about 43 MPG to 36 MPG on cheap stuff, 38 or so on 93 octane. The car does ping with the advance I run on cheap stuff, if I set the ignition advance to factory spec MPG takes even a bigger dive. Ethanol was a big downer for me and my HX.

Question for people with a ScanGauge, does it show you when the car is in leanburn? Most foreign cars have a MPG light that lets the driver know but it does not come on a US spec HX or any other lean burn US spec car that I know of... bummer.

[gone-ot]

...I watch the "instantaneous" MPG numbers, when they suddenly jump from 35-40 MPG up to 50-55 mph during normal, level, driving, I assume my 1.8L Vibe engine with SIDI has computed it's OK to run lean...and is doing so.

[redyaris]

What I was told in trade school was that regular has more energy and a higher rate of flame travel. Premium fuels have less energy and a lower rate of flame travel; less propencity to knock. Alcohole in fuel improves completeness of combustion. Alcohole does have less energy than gasoline which may be the cause of loss of fuel economy. I suspect that how the engine responds to E10 fuel is a function of wheather the engine was designed with that fuel in mind.

[Nden]

resurrection here.. but maybe Tomo knows? I just got a used Crane Hi-6 CDI system for my lil EG Vx with external Crane coil. It made his idle much smoother and stuff, but i think he only got 1-2mpg increase..which was negated by him driving faster! Will this be bad for the VX since I have lean-burn Fedal ECU? I'm using NGK sparkplug wires... and Iridium plugs. Perhaps a step colder heat range if I use this CDI system?
thanks for input guys.

PS. with some 14" 185 tires in front, 13" VX stocks in rear.. I'm getting about 40mpg with majority freeway driving. I try to keep it under 70mph w/VX 5spd.