[s5s]

Hi all, I've got a e90 330 with the N53 engine. Unfortunately on a few of my drives I have long sections of 20mph roads. If I am in 2nd, I am around 2000rpm and the car shows about 25mpg. If I am in 3rd I am around 1.3k-1.5k rpm and my car shows ~ 45mpg.

Are the low revs bad for the engine? In general what RPM should I be targeting for a long stretches of driving at the same speed? For example, on 40mph roads I can be in 3rd ~ 2500rpm or in 4th ~ 2000rpm. I tend to shift up these days because of lower noise and hopefully better mpg but I'm not certain if the lower rpm is harming the engine.

[Malteser_wfj]

Driving at anything above 1000rpm is absolutely fine.

If you're really worried, turn on the gear change indicator and just follow what the car tells you to do.

Edit: is this your first car?

[Silver Streek]

I would be driving in 3rd, especially as you are getting 20mpg higher.

[0l0dom0l0]

The low RPM doesn't harm anything, 20 in 3rd, 30 in 4th, 40 in 5th, I do 50 in 5th on country roads or 6th on the motorway. Anything above that its 6th.

They will cruise happily at 1200rpm all day long. The engine is under virtually no load at 20 or 30mph.

[s5s]

Originally Posted by Malteser_wfj

Driving at anything above 1000rpm is absolutely fine.

If you're really worried, turn on the gear change indicator and just follow what the car tells you to do.

Edit: is this your first car?

Not my first car but it is my first BMW and my first car with a proper engine. And it's the first time I've had to drive at 20mph for extended periods of time. I'm yet to find anyone who agrees with the 20mph limit yet somehow here we are (democracy?).