On 04/03/2021 11:06, Chris Hogg wrote:
On Thu, 4 Mar 2021 10:54:54 -0000 (UTC), jon wrote:

On Thu, 04 Mar 2021 09:54:20 +0000, Chris Hogg wrote:

I always thought the smell of the exhaust of high-performance engines
such as in sports and racing cars at hill climb meetings etc was due to
the use of 'Castrol' somewhere in the fuel mix (whatever Castrol was),
but I'm probably wrong.

Lead in the petrol caused the sweetnes, Castrol was a vegetable oil used
in racing and left a very distinctive smell when burnt.

But until a few decades ago nearly all petrol contained lead, lead
tetraethyl, as an anti-knock additive, and I wasn't conscious of car
exhausts smelling particularly sweet.

They didn't. The lead came out as a simple oxide.