Petrol or diesel - which warms up quickest? | Ask Honest John

Petrol or diesel - which warms up quickest?

I want to buy a new car that will be mainly used for journeys of about 10 miles each way with the occasional longer journey of 150 miles each way. Should I buy a petrol or diesel engined car as I want to keep my overall costs down.

The difference between the diesel and petrol versions of the car I have looked at is 60.1mpg to 44.5mpg, which seems a lot. Also the CO2 emissions are higher for petrol and so VED is higher.

Would I be losing out by buying the (cheaper) petrol version as I thought petrol engines needed longer to warm up?

Is there a formula for working this out?

Asked on 11 August 2012 by vedbed

Answered by Honest John

Petrol engines warm up faster than diesels because they are less thermodynamically efficient. Petrol turbos with water cooled turbos heat up fastest because of the heat exchange to the coolant passing through the turbo. which is turned by hot exhaust gases. The downside of diesels are the many expensive things that go wrong: dual mass flywheels, diesel particulate filters, EGRs as well as turbos and timing belts.

Tags: efficiency petrol or diesel?

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