The ideal RPM range

My husband thinks I’m ruining the transmission by driving our 2004 Audi A4 between the 2 and 3 mark on the rpm dial (more often closer to the 2…). He generally drives it higher than the 3 mark. I was taught by my dad that a reasonably lower rpm is actually better for the engine and saves gas. Who’s right…dad or hubby? Thanks.

Your hubby is NUTS. On my truck when in 5th gear the RPM is around 1800 at 65…1500 at 55. Your dad is 100% correct.

The ONLY problem is with a manual tranny…and keeping it TOO low then trying to accelerate in that gear it can cause severe knocking. However…2k is NOT too low. And if you really need to accelerate…down-shift.

You and your dad will get better mileage and longer engine life. Just don’t keep the rpms so low that the engine lugs (that will damage the engine). Neither high nor low rpms will do anything bad to the transmission. What the *&)#(^ is your husband thinking?

As long as the rpm stay under the red line and high enough that the engine doesn’t buckle (aka lugging the engine) you will not hurt the engine/transmission or affect its life expectancy significantly.

The engine will most probably out live the car’s body in any case. Just drive it the way it feels right to you and don’t worry about your husbands driving habit.

I’m an automotive designer if that matters… :o)

If driving the way your dad does “ruins engines” then my personal vehicles sure have a funny way of showing it. BTW, I used to think like your husband, and I cringed at the way my grandfather drove his vehicles, until much later in my life when I realized the he was the one who owned a pickup truck older than me that hasn’t needed a rebuild yet and I was the one who always had his engines apart.

Your husband is probably a gearhead who understands that engines have a “powerband”, a range of rpms where the engine makes its most torque and power and he dogmatically thinks the engine must always be in that rpm range. What he doesn’t understand is that most all dyno charts show the horsepower and torque measured with the throttle wide open and it is completely irrelevant to part throttle operation.

Below is a horsepower chart of a typical car engine that was measured at half and quarter throttle as well as full throttle. Notice that the max horsepower at half and quarter open throttle happens at a much lower rpm than the maximum horsepower at full throttle. This is one reason why automatic transmissions are programmed to shift at a lower rpm when the throttle is closed more.

There is no ONE right answer. In general I agree with advice you have received, but it is just not that simple. The specific engine, the weight of the vehicle, the road (Up hill or down) the load in the vehicle etc all enter in.

That said, assuming you don’t overdo it either direction, the differences are not going to be a big as many people expect.

I was taught by my dad that a reasonably lower rpm is actually better for the engine and saves gas.

Dad taught you well and you did well be remembering that word “reasonably.”

Now for the real question. You live with your husband and not likely your father. If this is your husband’s only fault, be very very happy and treasure him. don’t say a thing, maybe even drive his way, when he is in the car.

Doesn’t max HP occour at at a certian RPM regardless of throttle postion? Furthermore the torque and HP curves always meet at 5250 RPM. I don’t think your chart is accurate

Throttle opening will affect volumetric efficiency at all rpm (that’s its function actually) so the peak torque and peak hp will move up and down along the rpm range.

The 5252 cross point is a factor of the units being used and as such will not change.

Your husband needs to grow up and stop pretending he’s Michael Schumacher! The car is NOT a Ferrari, and he is not in a race!

This graph doesn’t show torque, if you want that, take the horsepower numbers and divide by rpm and then multiply that answer by 5252 or (33000/2pi) if you want to really be exact.

Note, the bottom graph shows brake specific fuel consumption, not torque. BSFC is seldom measured in a typical hot rod magazine dyno test.

Maybe just have your trusted mechanic just disconnect that tach and tell your husband “gee honey, I don’t know, it just stopped working”.

reving the engine over 3000 RPM will not hurt anything. It’ll use more gas, but it won’t hurt anything. If the A4 one with the turbo VW engine, he may just be trying to keep the turbo spun up :slight_smile: It’s hardly worth arguing over.

Boy! Thanks to everyone for all the information…some I don’t even remotely understand. I guess I need to boil it down here. I won’t lug the engine, and I think I’ll do my best to drive his way when he’s in the car. He is a pretty great guy, even worth any savings in gas.

Long story short…your pop is correct and hub owes you flowers because you are right and real men sent flowers for no reason at all.

This is not a technical problem. Both shift methods will be fine for getting long life expectancy out of your engine.

It’s not a technical problem because even if one shift method did cost you engine repairs, that money pales in comparison to the value of a healthy relationship with your spouse.