MPG + Heat
- Thread starter ste_bla
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Ah when the rad hose was leaking the temp gauge was 90 odd and now its fixed its 80 which is better and the misses said the last few weeks (when the hose started to go) its been dreaking more petrol (i hardly use the car)
Overheating means clearances in the engine that are correct under normal temperature conditions can close up and increase frictional losses. Oil can start to break down under high temperatures and pressures, further increasing friction. Hot engines mean high intakes temperatures which means more possibility of detonation, so ignition is retarded.
All of these will hurt economy, not help it.
All of these will hurt economy, not help it.
80 is a perfectly normal temperature for a car to run at.
120+ is usually where things start getting smokey.
that's massively overheating at which point yes things go to pot. but a engine slightly overheating does do better mileage, for a little while anyway. there have been super heated engines/fuel systems achieving crazy mileage, not that we will ever see such systems on the road.
iam trying to find a link to a superheated engine that ran upto 85mpg, il edit a link in if i find it.
Thats odd, my truck certainly likes a cold damp morning - The MPG is still circa 8 MPG but it pulls considerably better ,imo, than it does on a hot dry day.
Associate
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you sure it isnt colder = colder more dense air in easier to ignite, burns better, more efficient.
however in return in colder weather there is less grip etc effecting driving style running in higher gears to aid traction etc and running the heater / demister putting more load on the engine resulting in lower enonomy
think its better if the engine is hot but the air going in is cold im not 100%
Running the coolant hotter means that less heat is taken from the combustion chamber by the coolant and more energy is available for driving. Modern BMWs use a two stage thermostat system that runs the engine hotter when under low load for efficiency but cools more when under load.
Winter fuel economy is lower as engine spends longer warming up and hence running richer, plus things like wheel bearing grease takes longer to warm and thin out. Also, as the intake air is denser you don't need as much throttle for a given air mass to enter the engine which actually leads to greater throttling losses (well on petrol cars anyway).
Soldato
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Depends how much it's overheating by.
Engines only run at around 100*C because of the boiling point of water, if water boiled at 200*C we'd run engines up there somewhere, it's more efficient.
But... engines that are designed for 100*C will begin to bind up in places not too much beyond 100*C.
Engines only run at around 100*C because of the boiling point of water, if water boiled at 200*C we'd run engines up there somewhere, it's more efficient.
But... engines that are designed for 100*C will begin to bind up in places not too much beyond 100*C.
Most cars run a pressurised cooling system, which allows the temperatures to go higher than 100 without it boiling.
antifreeze* raises the boiling point to about 105 and running the ssytem under pressure like all cars do now raises it more.
the bp of a new car with good antifreeze can be around 115.
*presuming you actually have any and its still doing its job.
the bp of a new car with good antifreeze can be around 115.
*presuming you actually have any and its still doing its job.