Cruise control and new cars

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Sat 20 Oct 2007 20:53
Cruise control and new cars - OldSkoOL
I was always told not to use cruise control for the first 1000 or 2000 miles because its bad for the engine to run at the same speed as the engine needs to vary its revs.

Does anyone else follow this same principle? I would like to know if you can overuse cruise control; i have only done 4500 miles so far and i've started using it a lot of the time. Is it safe to do so or should i let the engine loosen up a bit?

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Sat 20 Oct 2007 21:35
Cruise control and new cars - cjehuk
I use mine all the time on the Audi TT and have since it was about 100 miles old. There appears to be nothing wrong with performance and at 5000 miles it's used no oil and doing nearly 40mpg. If you are worried stop, but from a technical perspective as an engineer in aerospace, I wouldn't be worried.
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Sat 20 Oct 2007 22:48
Cruise control and new cars - Number_Cruncher
>>Does anyone else follow this same principle?

If you are going to use the car on cruise control set to a specific speed for most of the time, then it makes really good sense to run the engine in at this speed.

Number_Cruncher
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Sun 21 Oct 2007 23:05
Cruise control and new cars - Happy Blue!
NC

I understand your concept of running a vehicle in, but unless you can determine that say 80% of the car's running will be at a given speed +/- 10% surely it is better to run a car in using HJ's recommended method of varying revs; using as high revs as is reasonable for the newness of the engine and definately not sitting the car at a fixed speed on the motorway when it is quite new.

Comments?
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Mon 22 Oct 2007 00:07
Cruise control and new cars - Number_Cruncher
>>Comments?

As you know, I'm not a big believer in running in - I'm of the start as you mean to go on school of thought.

My experience running hydraulic motors in suggests (via measurements of oil usage, torque produced, and motor efficiency) to me that running in "off-design" isn't helpful. The sealing surfaces in the motors were between the tips of th gears and the aluminium bore. Under different operating conditions, the gears run in different locations, and make different wear patterns.

For most drivers, I think there's no need to modify your driving style significantly during running in. The only modification I would give to that is for habitual mimsers to actually give their new engine a bit of a trashing instead of being even more sluggish.

My reason for saying this is that OEM cylinder machining methods are vastly superior to when running in was absolutely necessary - the oil bearing properties of various types of machined finish are now better understood, and can be made using the cylinder honing tools available to engine manufacturers.

Engines which have been re-conditioned will not have this expensive plateau honed finish, and these should be run in using more traditional methods - because the pistong rings and bore will initially only fit where they touch, and the cylinder finish will not hold oil as effectively as a properly manufactured bore.

>>HJ's recommended method

I would love to see the test results which back up HJ's claim.

Number_Cruncher
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