Running In An Engine
07 July 2004, 11:19 PM
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Running In An Engine
OK, here goes.
I have been doing some research on the best techniques for running in a new engine, but there seems to be an awful lot of disagreement out there.
According to many manufacturers’ manuals, the general advice is not to accelerate too hard, to vary the revs used, and to keep it below a certain rev limit, for a certain period of time. In the case of the Impreza, that's 4000 rpm and 1000 miles - I think that's fairly uncontroversial?
Where the problem seems to creep in is in the interpretation of those instructions. To me and, apparently, quite a few other people, they would imply that you should drive the car fairly gently to begin with. However, there is a fair amount of evidence that says that's not quite correct.
The 4000 rpm limit is, apparently, quite significant. The reason is that this is the point (roughly) where the engine is producing most torque. This means the highest pressure within the cylinder, which causes the fastest and best seating of the piston rings. Higher rpms have less pressure, but produce more heat – that’s why they should be avoided. Lower rpms don’t produce as much pressure, so the rings don’t bed in as quickly or as neatly. Worse than that, if the revs are usually kept below the limit during running in, the microscopic roughness of the cylinder wall will not be smoothed properly by the piston rings, and will instead become clogged with oil that seeps up (glazing). This prevents further bedding in, and leaves an inefficient seal that will ultimately result in an engine that produces less power than it should.
OK, that could be complete tosh, but it does sound feasible.
The conclusion I am coming to, from reading a whole bunch of advice and opinions on the matter, is that the best way to run in a car goes something like this:
1) Warm the car up thoroughly before setting off.
2) Don’t do any launches or boot it in 1st.
3) Using 2nd, 3rd and 4th if you can, accelerate using about 60% - 70% throttle up to the 4000 rpm limit.
4) Take your foot off the throttle and decelerate using engine braking alone (the vacuum in the cylinder caused by a closed throttle is equally important in the running in process because it draws oil up to flush away the tiny metal filings being skimmed off).
5) Rinse and repeat.
6) Change oil at around 100 miles. Use mineral-based oil, not synthetic.
7) Change oil again at 500 miles. Use mineral-based oil, not synthetic.
8) After 500 miles it’s OK to stray above the 4000 rpm limit occasionally since, if you have done the previous 500 miles properly, your engine will be at least 80% run-in by now and you will be on very clean oil. No red-lining it though.
9) Change oil again at 1000 mile service. Still avoid fully-synthetic oil until at least the next scheduled service.
10) OK, you’re now free to go.
Now, this may not be entirely practical, and could even be dangerous if it’s done in traffic (or in front of police!). But, in theory…
What are people’s thoughts on this?
I have been doing some research on the best techniques for running in a new engine, but there seems to be an awful lot of disagreement out there.
According to many manufacturers’ manuals, the general advice is not to accelerate too hard, to vary the revs used, and to keep it below a certain rev limit, for a certain period of time. In the case of the Impreza, that's 4000 rpm and 1000 miles - I think that's fairly uncontroversial?
Where the problem seems to creep in is in the interpretation of those instructions. To me and, apparently, quite a few other people, they would imply that you should drive the car fairly gently to begin with. However, there is a fair amount of evidence that says that's not quite correct.
The 4000 rpm limit is, apparently, quite significant. The reason is that this is the point (roughly) where the engine is producing most torque. This means the highest pressure within the cylinder, which causes the fastest and best seating of the piston rings. Higher rpms have less pressure, but produce more heat – that’s why they should be avoided. Lower rpms don’t produce as much pressure, so the rings don’t bed in as quickly or as neatly. Worse than that, if the revs are usually kept below the limit during running in, the microscopic roughness of the cylinder wall will not be smoothed properly by the piston rings, and will instead become clogged with oil that seeps up (glazing). This prevents further bedding in, and leaves an inefficient seal that will ultimately result in an engine that produces less power than it should.
OK, that could be complete tosh, but it does sound feasible.
The conclusion I am coming to, from reading a whole bunch of advice and opinions on the matter, is that the best way to run in a car goes something like this:
1) Warm the car up thoroughly before setting off.
2) Don’t do any launches or boot it in 1st.
3) Using 2nd, 3rd and 4th if you can, accelerate using about 60% - 70% throttle up to the 4000 rpm limit.
4) Take your foot off the throttle and decelerate using engine braking alone (the vacuum in the cylinder caused by a closed throttle is equally important in the running in process because it draws oil up to flush away the tiny metal filings being skimmed off).
5) Rinse and repeat.
6) Change oil at around 100 miles. Use mineral-based oil, not synthetic.
7) Change oil again at 500 miles. Use mineral-based oil, not synthetic.
8) After 500 miles it’s OK to stray above the 4000 rpm limit occasionally since, if you have done the previous 500 miles properly, your engine will be at least 80% run-in by now and you will be on very clean oil. No red-lining it though.
9) Change oil again at 1000 mile service. Still avoid fully-synthetic oil until at least the next scheduled service.
10) OK, you’re now free to go.
Now, this may not be entirely practical, and could even be dangerous if it’s done in traffic (or in front of police!). But, in theory…
What are people’s thoughts on this?
Last edited by WR1 Wannabe; 07 July 2004 at 11:47 PM.
07 July 2004, 11:23 PM
#2
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Simple rule is a 500 miles per thousand revs.
Don't accelrate too hard until 3k miles
DO NOT warm the engine up then drive away. Reason being, engine is hot, oil is cold - damage. Just turn on and drive steadily away.
Just don't thrash it until 4k or so miles. Mechanical sympathy. Particularly if its a scoob.
Don't accelrate too hard until 3k miles
DO NOT warm the engine up then drive away. Reason being, engine is hot, oil is cold - damage. Just turn on and drive steadily away.
Just don't thrash it until 4k or so miles. Mechanical sympathy. Particularly if its a scoob.
07 July 2004, 11:28 PM
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Sounds feasible. That's what I'm doing more or less minus the extra oil changes. I don't think its right to warm the car up before setting off, gentle driving should be adequate.
Jason
Jason
07 July 2004, 11:29 PM
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Having run in a lot of cars over the years I can say things have changed with modern engines.
My advice is, for first 500 miles try not to go over 50% max revs. Ensure engine is warmed up properly (water temp does not indicate oil temp - oil takes 3x longer to warm up).
At 500 miles change the oil and filter.
Increase revs to 75% max for 500 miles.
At 1000 miles drop oil again if you are paranoid and then let her rip.
This is not all to benifit the engine, its brakes, clutch, diff, propshafts etc etc.
I have only had an engine blow once - in a hire car, on motorway, come off slip road (car had about 90 miles on clock) and reved to maybe just short of the red line on the down change and BANG! F1 style plume of smoke and some funny looks from other drivers. Ooops!
My advice is, for first 500 miles try not to go over 50% max revs. Ensure engine is warmed up properly (water temp does not indicate oil temp - oil takes 3x longer to warm up).
At 500 miles change the oil and filter.
Increase revs to 75% max for 500 miles.
At 1000 miles drop oil again if you are paranoid and then let her rip.
This is not all to benifit the engine, its brakes, clutch, diff, propshafts etc etc.
I have only had an engine blow once - in a hire car, on motorway, come off slip road (car had about 90 miles on clock) and reved to maybe just short of the red line on the down change and BANG! F1 style plume of smoke and some funny looks from other drivers. Ooops!
07 July 2004, 11:38 PM
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I don't think there is a text book way to run in an engine !!
Common sense must prevail and guidelines adhered to - as I understand it the 1000 miles is critical to 'bed in' all the components.
Spot on with oil types for the running in period but not so sure about the need to do a 100 and 500 miles oil change - the heavier oil will carry any metal bits to the filter.
Vary your revs building up to the 4000 revs without booting it. Increase the build up to 4000 rpm gradually over the 1000 miles. Change oil and filter, 5/50 Valvoline racing oil in and take the car up past the 4000 rpm mark gradually over next 500 miles or so and then ............................
Thats how I'll be doing it very shortly anyway !!!!!
Common sense must prevail and guidelines adhered to - as I understand it the 1000 miles is critical to 'bed in' all the components.
Spot on with oil types for the running in period but not so sure about the need to do a 100 and 500 miles oil change - the heavier oil will carry any metal bits to the filter.
Vary your revs building up to the 4000 revs without booting it. Increase the build up to 4000 rpm gradually over the 1000 miles. Change oil and filter, 5/50 Valvoline racing oil in and take the car up past the 4000 rpm mark gradually over next 500 miles or so and then ............................
Thats how I'll be doing it very shortly anyway !!!!!
Last edited by MarvSTi5; 07 July 2004 at 11:40 PM.
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07 July 2004, 11:41 PM
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regarding oil - if this is a new subaru you are talking about only put in it what subaru say - other wise bye bye 36 month warranty if they find out...
And all this 3000 and 4000 mile stuff - not really going to make any diff - so long as it dont break in the first 500 miles you are reasonably safe. The old theory used to be to "run" the engine for 24 hours (obviously not in one go) - after that you should be ok. Some engines are bench run in these days btw.....
And all this 3000 and 4000 mile stuff - not really going to make any diff - so long as it dont break in the first 500 miles you are reasonably safe. The old theory used to be to "run" the engine for 24 hours (obviously not in one go) - after that you should be ok. Some engines are bench run in these days btw.....
08 July 2004, 07:15 AM
#9
I think you have all missed one point.
Never labour the engine in any gear, hot or especially cold.
I have known people here at work with Company cars who run-in their AUDI's etc across the forecourt after taking delivery.........then they let rip.
Drive gently, opening up bit by bit, warm from start-up by driving down the road, follow Manufacturers oil grades/schedule and at 5000 mile its done, and enjoy the Scooby for what it is, a bloody fast thrill of a car!
911
Never labour the engine in any gear, hot or especially cold.
I have known people here at work with Company cars who run-in their AUDI's etc across the forecourt after taking delivery.........then they let rip.
Drive gently, opening up bit by bit, warm from start-up by driving down the road, follow Manufacturers oil grades/schedule and at 5000 mile its done, and enjoy the Scooby for what it is, a bloody fast thrill of a car!
911
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