Your Opinion Wanted - RPMs vs Engine Load

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OriginHacker21

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Location
High Desert, California
Engine: 2.2L Ecotec manual tranny with Amsoil SSO 0w30.
Scanguage II

Every day I drive up the 15 freeway - about 5 minutes of uphill (and downhill on way back).

Your Opinion Wanted:

1. Drive up in 5th gear at 89% engine load and 2400 RPMs

OR

2. Drive up in 4th gear at 70% engine load and 3500 RPMs.


Which is easier for the engine and/or oil life? The engine is approaching 114,000 miles - just want to do whats best for it.

What is your opinion? What would you do?

Thanks for the comments/help.
 
I don't have too much technical/engineering knowledge, but the way i understand it is that option 'A' is a bit harder on your engine, mainly bearing, b/c you are going at a slower RPM, and closer to 'lugging' it; whereas option 'B' you are at higher RPM's, so the engine is more in its 'operating range', and the only penalty is fuel mileage.....have I got it right?

Anyway, I 'used' to be an option 'A' person - RPM's are bad, and wore out an engine, so I would have run it slower for peace of mind. These days, however, I know RPM's aren't as hard on modern engines, so I would take option 'B', and keep the engine more into the power band. But option 'B' costs you (these days) expensive fuel...
 
I was thinking #2 would be better, assuming every thing's warmed up, otherwise the oil will be thicker and the oil line might already be in bypass so as not to gain any extra replenishment flow to the bearings (in which case I would probably opt for #1, though still cringing at the thought of demanded output percentages while still "cold"), etc. Extreme case would be over pressurization and cavitation but I think multi-grades have helped to lessen the likelihood under "normal" driving circumstances due to their capacity to shear more than straight grades.?.
 
Good note on power/efficiency band Harley Anderson. Another good overall reason.

Just a few examples of the many operating variables that play out without much if any thought to the average operator.

Take care.
 
The MPG difference is like 22mpg (#1) vs 17mpg (#2). So it isn't that bad - its only for 5 minutes too.

Thanks for the replies - Always wondered if having higher load was more wear and tear vs a higher RPM but less load.


BTW - my work commute is 2 hours - I hit this 5 minute uphill drive about 1 hour into my drive so the engine is warmed up as well as the oil. :)
 
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I say option 1 (if it is in the operating range of your bike), unless you try to pass someone then yes you are going to put a "strain" on the rod(s) and bearing more because the engine has to try and "push the bike" in a lower RPM range. If you are just putting down the road, not going up hills, passing people etc, then there is no real extra "strain" on your engine.

Going up hills, passing a lot, etc, use option 2
 
I'd guess peak torque comes at about 3000 rpm. so either gear would proberbly be OK. However if the oil is not up to full operating temperature (30 minutes driving) I might go option (B)
 
If it were my car, option 1 without hesitation.

As long as there are no signs of distress like pinging or overheating, go for it.

Thank for posting the Scangauge MPG numbers for the two conditions. It helps kill that old wives tale about peak fuel efficiency being at peak torque rpm.
 
I love this question as it's something I've spent more than a healthy amount of time thinking about in the recent past (a large percentage of my 20 mile round-trip commute every day is traversing a 2-3 mile hill both ways).

I go with option 2 in my car. 3500-4000 RPM doesn't seem like too much for a 4 banger to take, and in my particular case to go up in 5th I'd have to keep it floored just to maintain speed. My car is a civic, so it's a little more torque-challenged than your ecotec. How much does it feel like you're pushing your car when you go up in 5th?

Even when I was driving my 280zx (more torque and lower peak than your ecotec) the car would only just barely ride up the hill in 5th gear at 2900 RPM or so and felt a lot healthier at 3500 in 4th. Of course, we're talking about different hills...

At any rate, I vote for the 4th gear ascent.
 
Another vote for 4th gear ascent.

Can that scangage show the % throttle opening? The lowest throttle opening required to maintain speed on the hill might be your best bet.

On second thought... the seat of your pants is the best bet. Ain't no computer been invented that'll do better than that (yet).
 
Option #2 is easier on the engine especially if the oil is not quite up to temp. Also at the higher RPM you’re getting more oil flow and better cooling and if you hit a gust of wind you are in a much fatter part of the torque curve which is easier on everything. If this is a frequent commute this kind of stuff gives you something to think about too.

Is this the grade near Temecula?
 
Originally Posted By: tom slick
I vote that it doesn't make a danged bit of difference.


That makes it an ideal topic of discussion for BITOG.
grin2.gif


It will get worried to death. Unfortunately it will be a slow painful death.
 
Since people seem to be worried about fuel economy for 5 minutes of driving I say go uphill in 4th gear and coast down the other side in neutral.

Clark
 
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