Running uphill in 6th gear == bad for oil?

[blackman777]

Well I got scolded. I was running up a mountain in 6th gear, and had my foot mashed to the floor to get wide open throttle (WOT). The car was weak in torque, but it did gradually accelerate from 65 to 80 (at the peak).

Supposedly doing this "lugs the engine, scrapes the oil off the cylinders, and wears the metal". The engine was spinning at 2500 to 3000 rpm so I didn't consider it to be lugging, because I thought that only happened below 2000. Does the oil really fail to protect in this situation?

Thanks

 

[Lead Shoes]

The only thing you were doing is wasting fuel.

CarNoobie is that you?

 

[supton]

What car and what engine?

I sincerely doubt you lugged the engine. The engine is running at a good clip and isn't making a lumping sound, like it does at low rpm lugging. I don't think you can lug at those engine speeds (again, general sense), engine is running too fast and the oil pressure is good. Even if the engine loses speed at full throttle, it's not lugging.

OTOH at low engine speeds lugging will be felt and heard, and you'll definately need to downshift.

 

[supton]

How is that wasting fuel? Full open throttle means less pumping losses (not pulling air over a partially closed throttle plate).

 

[badtlc]

Your owner's manual should outline what to avoid in those situations.

 

[eljefino]

It would have been better to drop to 5th and run 80% throttle.

The fuel enrichment could wash down the cyl walls a little.

The biggest load possible was on your con-rod bearings, though oil pressure was probably okay.

Your PCV system was in "blowby mode" where stinky air goes through the fresh air tube "backwards" and soils your throttle body. Also, lacking vacuum, your rings might not have sealed that perfectly.

I'm not sure what your objective was, but you probably would have saved gas and engine wear in 5th gear at 80% load. Yeah it "sounds worse" on some cars to let them rev, or some engine types would vibrate a bit.

The definition of lugging is if your cam and valves can't use more air to make more power even if you open the throttle more. I don't think you were "there."

I'm going to stick this BSFC map in. I can only begin to explain it.

Basically it's a map of engine efficiency for input vs output, your scenario puts you in or near the "red blob" assuming your engine is cammed/ valved/ set up like a Saturn 1.9 16V. This sort of applies for many econo box normally aspirated smog american motors.

PS I put a "wrong" transmission with shorter gearing in a saturn I fixed up for my brother and got 42 MPG at 65 MPH. "Pumping losses" are slight, especially with EGR "leaking vacuum", and IMO come up mostly with people looking for an excuse to speed.

 

[blackman777]

Originally Posted By: Brenden
CarNoobie is that you?


HA! No but I guess I am a newb. I thought wide-open throttle was the engine's most efficient state (like a diesel: no pumping losses).

In general I try to avoid shifting so I don't wear-out the clutch and have an expensive $1000 clutch replacement later on
.

 

[440Magnum]

Originally Posted By: Brenden
The only thing you were doing is wasting fuel.

CarNoobie is that you?


Actually that's close to the most fuel-efficient way to climb a hill (except for the topping out at 80 mph part...). Backing just off WOT is probably better, since some engine management systems come out of closed-loop when they detect complete WOT. But keeping the throttle open eliminates pumping losses and the high cylinder pressure increases burn rate and efficiency, allowing the timing to retard a little so that less time is spent working against the rising piston.

As for longevity- its not that big a deal for most engines, unless it starts triggering pre-ignition which is hard on bearings already loaded heavily by the lugging.

 

[Hokiefyd]

Originally Posted By: blackman777
I thought wide-open throttle was the engine's most efficient state (like a diesel: no pumping losses).


In theory it would be, but most fuel injection systems will enrich the mixture at and near WOT to keep combustion chamber temperatures in check.

That said, I wouldn't say that 2,500 to 3,000 rpm is lugging the engine.

I'd also suggest that flooring the car on a long hill, accelerating from 65 to 80 mph, is not the best way to maximize fuel economy.

 

[SwampSurvivor]

I'd be afraid of it pinging on a hill. Automatics won't do it as they'll kick down, but I've rode with a few people who did this tactic and I could hear them pinging and knocking all the way up the hill!

What was the engine in? I wouldn't worry about doing this in a truck or something with a higher duty cycle, but a small aluminum 4 in an econobox ... I'd try to avoid.

 

[randomhero439]

Your fine, however you just wasted a good bit of fuel. In that low RPM, your car cant reduce the ignition timing enough to constantly be at WOT in low RPM, causing pinging. Too much pinging is bad. Dont worry about it

 

[supton]

Hang on--we don't know what engine this is!

My car redlines at 4700. 2,500 is a sweet spot and 3k is buzzy. It doesn't lug until I get below 1800 or so. I'd guess a lot of the older GM V8's would be quite similar. My engine may not be conventional but so far we're assuming that the OP has something likes to spin.

Clutches can be shifted lots and not wear out. If you are gentle on takeoff, and rev-match on shifts, it'll last a very long time.

 

[blackman777]

Jetta. I filled the tank with 91 last time so knocking shouldn't be a problem. The engine sounded nice and smooth. I don't shift down & up in order to avoid clutch wear/replacement. I just ride 6th gear all the way to work (unless there's a jam on the highway).

 

[supton]

2.5 or 1.8T or 2.0T or 2.slow?

 

[HerrStig]

Originally Posted By: supton
How is that wasting fuel? Full open throttle means less pumping losses (not pulling air over a partially closed throttle plate).
+ 1

 

[Lead Shoes]

Originally Posted By: HerrStig
Originally Posted By: supton
How is that wasting fuel? Full open throttle means less pumping losses (not pulling air over a partially closed throttle plate).
+ 1


Hitting WOT and going uphill to gain speed (60-80) is waste of fuel, can't believe you guys are even asking how that's a waste.

Originally Posted By: blackman777
Originally Posted By: Brenden
CarNoobie is that you?


HA! No but I guess I am a newb. I thought wide-open throttle was the engine's most efficient state (like a diesel: no pumping losses).

In general I try to avoid shifting so I don't wear-out the clutch and have an expensive $1000 clutch replacement later on
.



CarNoobie is some guy who posts questions like you just asked just to start arguments and troll.

If you are worried about wearing the clutch, rev match it by double clutching before you downshift, I don't do it to save the clutch, I do it for the synchros and so it doesn't jerk me forward.

 

[supton]

Sure, it's a waste. But what burns more fuel: WOT in a high gear, or half-throttle in a lower gear / higher rpm, with same acceleration rate?

 

[blackman777]

My theory (and it's probably wrong) is that 6th gear and WOT extracts every ounce of energy possible from each gasoline injection.

Shifting to 5th or 4th gear and having throttle at 50-60% does not (due to throttling losses & higher RPMs). Less efficient. Off to work.....

 

[Lead Shoes]

Originally Posted By: supton
Sure, it's a waste. But what burns more fuel: WOT in a high gear, or half-throttle in a lower gear / higher rpm, with same acceleration rate?


There are way too many variables involved in that scenario....

 

[Quattro Pete]

Originally Posted By: supton
2.5 or 1.8T or 2.0T or 2.slow?

The 2.slow and the 1.8T Jettas never had a 6-speed manual, so it'd have to be one of the other two.