The Rover was treated to some nice new oil on Friday ater 10 months and about 12k miles.
I'm convinced it runs smoother now.
Is it my imagination?
If not is the effect caused by the hydrolic tappits working better?
--
Parp, Parp!
Note: All Toad posts come with an implied smiley.
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My Saab 9-5 (1999 2-litre, 83k miles at the time) seemed to run noticeably better after a minor service of which an oil change was the highlight. As far as I know, nothing else was touched.
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I have often noticed this effect, with a variety of cars, none with hydraulic tappets. I have wondered whether it was just psychological, but I think it is real.
The main effect I notice is that the engine seems to be quieter, so I wondered whether oil thins with age? If true, it does so after a very small mileage - I always change mine at 3-4,000 miles, yet still the effect is noticeable.
Maybe there are other factors at work, depending on the engine. eg, on carburettor engines I always take the opportunity of topping up the dashpots, and this definitely improves running and performance.
Perhaps the oilchange coincides with little but significant actions like this?
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I have experienced exactly the same, and more so when I put cheap (thicker) oil in the car - so its quite likely that oil becomes less viscous with time (and miles). I just had Mobil 1 in the Omega and couldnt notice any difference, except a little quieter on start up. This i would expect as mobil 1 is very thin and makes it way to the head quicker I assume.
A clean filter should improve the speed that oil is distributed around the engine, and therefore should result in quicker settling down of the engine. Also I wonder if old oil gets hotter than new stuff, because of its specific heat value. This would also affect its viscosity, and lead to smoother running - especially on a high miler.
I did try that slick treatment many years ago in my cavalier, didn't make any difference other than give me an oil leak!
S,
_____________________________________
SVPworld (incorporating PSRworld)
www.svpworld.com
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SVPw,
Actually, a blocked filter makes no difference to the speed of the oil through the engine because oil is virtually incompressible and will find its way through somehow, even if only via the filter by-pass circuit. I'll illustrate this with an example! ...
A friend bought a reconditioned engine for his Morris Minor many years ago. This engine has a pressure relief valve in the side of the cylinder block consisting of a drilling and a spring-loaded shuttle which slides to uncover a port when the oil pressure is above a certain value, such as when starting from cold. A second port allows the relieved oil to drain back to the sump. The reconditioners had sleeved the relief valve drilling to overcome wear but, as we were to discover, the sleeve blanked off the oil drain port. When my friend started the engine for the first time, the relief valve opened to lose some of the excess system pressure but the oil had nowhere to go and the rapidly rising system pressure blew off the oil filter canister with an almighty bang!
That was quite spectacular, as you can probably imagine. Even more so when you consider that the oil pump is driven directly from the rear end of the camshaft yet neither was damaged. The 'explosion' threw oil everywhere so the nice new engine didn't stay clean for long, and neither did we spectators!
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I thought it was accepted that mineral oil gets mechanically degraded (i.e. gradually broken down, reducing the viscosity) by the mincing effect of the engine, part of the reason why it has to be changed, and why the intervals are longer for synthetic oils which stand up to this treatment better. Or am I wrong?
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Andrew, I think your analysis is very close to the mark.
Polymers are added to multigrade mineral oil to control the viscosity but these degrade and burn, thus helping to clog the filter as well as reducing the viscosity of the oil. Hence the need for closely spaced oil changes with mineral oil (preferably 5000 miles or six months maximum, as often advised on this forum).
Synthetic oils rely very little on polymers, some not at all, and this is one of the reasons why oil changes can be considerably extended with those oils. This means that the cost-to-change can be very similar to mineral oil over time.
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Well, cars do have souls, ToTH. Imaging how it must be to be a car. Left out in the cold, fag ash and litter thrown inside, hauled out of bed at the owner's whim and expected to perform.
...and then this nice mechanic comes along and gives you a bit of TLC. A nice drop of new oil, looks at your creaking bits, attends to your flatulence, and probably rubs your chest with a nice oily rag.
Of course you'll run better!
;-)
Ian Cook
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Ian's right - what's more my old BX runs much quieter and better after a good wash and wax and when I've cleaned the windows! And she positively purrs when I say "Good old girl" after a trouble free long trip - or is that my wife? I get confused in my old age>> Steady !
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I used to change the oil on my Rover 218SLD Turbo every 3-4k miles, which was roughly once a month. My dad now has the car which has 210,000 on the clock and still going strong. From this I have learned that if you only do one thing to your engine, make sure it is an oil change.
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The partical polution of the oil, the black stuff, alters the transmitability of sound through the media and can and does change the note of the engine. Oil oil can make a car sound a little harse and new oil sounds smoother. As far are actully running better it probably does but I suspect you cound not measure. Having said that I had a A reg 83 volvo 240 carb job and at oil change the tick over would rise slightly with new oil, i.e. less friction. I don't go for this 20,000 oil change business. It depends on the use and temp cycles of the vehicle.
Regards
Peter
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I have always thought that when filling up with oil the rocker box becomes full for a few seconds and it is this that makes the top end initially quieter.
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