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MG MGF Technical - Mobil 1 and Rattles
This has been mentioned before, but now it's happened to me I'm showing more interest.
I've just had the F serviced, at 8,500 miles, and the engine was filled with Mobil 1. Now when I start it from cold there is a half-second or so burst of light rattling which wasn't there before. I assume that this is the hydraulic tappets pumping up to pressure, and I also assume it's caused by the thinner oil draining back from the tappets to the sump overnight. Does everyone using Mobil 1 get this rattling, and will it have a harmful effect on the engine?
I use Mobil 1 in my late '95 214 (extravagent. I know), and this is, at 50k, quite rattle-free when cold, a brilliant engine in fact. Both engines are using the standard Rover filter, GF280 or whatever it is. I don't like the rattle, if I can't live with it I'll go back to an oil with a higher W rating.
i had the same problem with my vvc cica 8000mls, about a month after oil change at dealers i got the same tappet noise. i dont know what oil was put in at the service but i changed it with castrol magnatec and the problem disappeard straight away and not heard since, mileage now over 10000
|I´m using Mobil1 0w40 trisythetic. It´s the thinnest Mobil1. Never noticed any strange noises! Last used Mobil1 15w50.|
Quite the opposite with mine. Before i had the Mobil 1 treatment there was always a slight rattle while the oil warmed up. Not any more, it would seem that as the oil is thinner it's doing it's job from the moment the key is turned. Did your dealers flush out the old oil before topping up with Mobil?
My noise is a sub-second light clatter on startup from cold, there is no permanent noise. It is the sort of noise that can be lost in the vigorous startup clamour of starter clashing with the flywheel gear ring, etc. However, I have been doing some probing, and asking some questions.
Although I don't have a detailed diagram of the hydraulic tappets, or their operation, I have sussed out the principle of operation which I won't drag out here (I would like to know what mechanism expands the tappets though).
I would think that over a period of hours the thinner Mobil 1 is bleeding from the tappets, as it's designed to do, possibly only in those under pressure where the valve is open. At engine startup there is a momentary light fizz as the oil pressure pumps up the tappets back to zero clearance.
I've spoken to a charming lady at Mobil's technical help line (I don't wish to be ungallant but at my age, >Dieter, <Ted, all women are charming) and the technical staff there say that there's no problem with this noise when using 0W-40, and it won't damage the engine. They also say that it is a good sign, as it shows that the oil is circulating inside the tappets, and this will prevent oil oxidisation over an extended mileage (I can't quite swallow that). Mobil 1 Motorsport 15W-50 could be used, and might stop the noise, but at the expense of ease of cold start and economy, etc.
My F was at the garage today to fix a slight leak from the cam cover (generously paid by Rover), and the head mechanic also said that there was no problem with this. So I'll go on my way for a while, and see if I can live with it.
So why don't I get this noise on my uncosseted 214 at 50K miles? Better tolerances? I just don't know.
|You could try sourcing your Mobil 1 from France, where the grade is 5W/50 and it is 30% cheaper :o)|
you could also nag Mobil to sell this grade in the UK...
|I have just had delivered a brand new VVC and the Lubricant Chart states that it MUST use a 10W-40 viscosity oil! |
PS The car did only 52 miles and then the ABS came on unexpectedly 'cooking' the discs. Car has since been rejected!
I can't recal from your previous posts whether your car is the 1.8i or VVC. If it is the latter then there is a different spec of tappet fitted to the MPi engines.
I certainly follow the comments that the oil is being removed from the tappets which are under valve spring compression for longer periods.
Of interest I was running a BRM up on Pete Burgess's rolling road last week and trying different simple mods. This car displayed slight tappet noise and in fact was not always smooth at certain rpms and throttle openings. One test involved using a fuel additive which had an amazing effect in making the engine noticeably quieter, smoother and gave an extra 3bhp.
Pete produced this and I can't remember the name, but on the way back to my place the difference in engine smoothness was maintained. We are waiting to see what happens with subsequent fill ups.
In this instance a change of fuel characteristic has altered combustion, which has altered the way the fuel is burned and the noise developed. Odd as it may sound but have you also changed fule suppliers at the same time as you changed the oil?
It's a 1.8, nothing too complicated. To repeat myself there's no tappet noise when running, just a momentary light clatter when starting from cold, although this seems to have diminished a little now. I start the car in a garage in a quiet area, so every noise is amplified. I'm not too worried now.
I try to use Shell petrol when I can, but their stations are few and far between, especially now the Bromsgrove station has closed. I'm still intrigued with the operation of the tappets, just for mechanical interest and curiosity's sake. I know that the inverted bucket has an internal plunger (the tappet itself) which is the bit that's pumped up to take up the clearance, but what the mechanism is I have yet to find out. Is there a small valve in the tappet? I'm OK with the theory, I want to see the bits!
I was rather envious of you running up a BRM, not the H16 surely, then I realised it was a Rover BRM, not quite the same. I saw the Yardley BRMs at Silverstone and Brands many years ago, can't remember the drivers, Pedro Rodriguez or JP Beltoise, and Ginther/Gethin? I think then they had given up on very complicated engines and were running V12s. I'm meandering here.
I'm not a fan of additives, but nevertheless I'd be interested to know the make of the stuff you put in the Rover. I've also been trying to fathom out whether those with oil overheating problems would be better off with Mobil Motorsport 15W-50, but I can't see any characteristic which would reduce the temperature - increase it more likely. Any thoughts anyone?
This thread was discussed between 02/04/2000 and 17/04/2000
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