do petrol engines warm up quicker - true or false ?

forgotmyname

This winter i will be doing the age of trick of a piece of cardboard
in front of the rad. Or partially covering the grill.

Knew i should have bought another petrol one. But close to 20MPG in
winter maybe a bit costly these days.

reeac

GolfBravo wrote: »

Answer: true.

Diesel engines are much more thermally efficient (up to 50% efficiency) than petrol engines (around 25% efficiency).

So diesels must give twice as many mpg. then. I don't think so.

General rule of thumb is: 2-stroke petrol: 10-12 bhp.hours per gallon, 4-stroke petrol, 15 bhp.hours per gallon
diesel 20-22 bhp.hours per gallon.

GolfBravo

reeac wrote: »

So diesels must give twice as many mpg. then. I don't think so.

You're confusing car mpg with engine thermal efficiency.

Diesel engine thermal efficiency is at least 30% higher that a petrol engine due to its very high compression ratio.

Petrol engines have lower compression ratios to avoid knocking = lower thermal efficiency.

Higher compression ratio = higher combustion efficiency.

colino

Good grief, would you random wiki!!!!!!s, googlegrabbers and searchshits leave one subject alone? Your lack of even basic engineering knowledge is laughable.