Engine oil

star100 · Post by **star100** » Sun Apr 22, 2007 4:53 pm

Hi everyone ive got a disco 3.9 on an N reg and it has done 142500 miles, just wondered what would be the best oil to use? Ive been using s 15/50 but someone told me i would be better using a 20/50 oil. Is that right?? I have noticed that when cold she runs great but when she has warmed up she is just starting to tap, would this be coz the oil is too thin for her? If anyone can help that would be great. Thanks Sarah

kiwicar · Post by **kiwicar** » Sun Apr 22, 2007 5:14 pm

Hi
at 145k miles I think there will be little difference with which oil you use, everyone recomends 20 /50 on here for the rover, and it is probably be the best, 15/50 20/50 there is little difference, the hot viscosity is what is important on an older engine. The ticking will probably be either a lifter that is worn and no longer pumping up fully or a warn cam lobe that the hydraulic tappet can no longer take up the slack on.
Change the oil regulaly and run it till you decide it needs a rebuild, you could freshen it with new cam and lifters, but I would wait until you decide it needs a full rebuild. (I think I may have repeated miself there

)
Mike

Post by **katanaman** » Sun Apr 22, 2007 5:17 pm

15/50 hot is the same thickness as 20/50 hot, its only when cold the 15/50 is thinner. You could try 20/50 but it shouldnt make any odds and to be honest at that mileage you are bound to have a few worn components in there. The bores on rovers last well but the crank and bearings can wear and the cam is specially prone to wear.

sidecar · Post by **sidecar** » Sun Apr 22, 2007 6:21 pm

Valvoline VR1 20/50 is a good oil to use as it contains a lot of zinc which keeps the valve train in good condition. It is for this reason that it does NOT have an API rating. (Zinc is good for cams but not quite as good for trees!) As its a 20 grade when cold you wil have to warm up the motor before giving it any stick! like others have said, its probably getting a bit tired in places.

star100 · Post by **star100** » Mon Apr 23, 2007 8:47 am

Thank you for your help, your all very kind. I will use a 20/50 on this oil change. Sarah

badger · Post by **badger** » Mon Apr 23, 2007 11:44 am

Hmmmm.... yours is an interim serpentine engine with the crank driven oil pump, yes? In which case the correct grade is 10W40 or 15W40, not a 50 grade. 50 is too thick in the later engines as they run tighter crank bearing tolerances and a higher pressure. With a thicker oil there is a possibility that the oil flow rate to the rear mains will be seriously reduced.

sidecar · Post by **sidecar** » Mon Apr 23, 2007 12:36 pm

Badger has a very good point. I was assuming that you have an older v8 like mine.

You should still try to find an oil that has a high zinc or phosphorous content has it protects the cam.

Post by **katanaman** » Mon Apr 23, 2007 1:15 pm

badger wrote:Hmmmm.... yours is an interim serpentine engine with the crank driven oil pump, yes? In which case the correct grade is 10W40 or 15W40, not a 50 grade. 50 is too thick in the later engines as they run tighter crank bearing tolerances and a higher pressure. With a thicker oil there is a possibility that the oil flow rate to the rear mains will be seriously reduced.

You have a good point (I thought it was the older pump) but I don't think this is the problem in this case. Its knocking when hot. I would expect an oil problem when cold with the thicker oil. Even if it is the newer pump it should easy be able to pump hot 20/50. I don't think the clearances are that much different either its just the pump is much more efficient so can handle the thinner oil.

ihatesissycars · Post by **ihatesissycars** » Mon Apr 23, 2007 1:53 pm

Do you know what the oil pressure is hot/cold + different rpms?

badger · Post by **badger** » Mon Apr 23, 2007 3:38 pm

HI katanaman, have a look at the manuals for pre and post serpentine engines, there's a fair difference on the clearance for the main bearings.

star100 · Post by **star100** » Mon Apr 23, 2007 4:22 pm

Hey everyone, well ive bought the Valvoline 20/50 and changed the oil. Ive done a good 150 miles this afternoon and now it seems to be running fine when hot, no taps just running normal. So maybe i had a lifter that wasnt pumping up fully and now it is??? Anyway thank you all for your advice. Sarah

sidecar · Post by **sidecar** » Mon Apr 23, 2007 4:46 pm

star100 wrote:Hey everyone, well ive bought the Valvoline 20/50 and changed the oil. Ive done a good 150 miles this afternoon and now it seems to be running fine when hot, no taps just running normal. So maybe i had a lifter that wasnt pumping up fully and now it is??? Anyway thank you all for your advice. Sarah

Hi Sarah,

Even if your motor should run on a 40 grade when hot I doubt that having a 50 grade in it will do it any harm at all. However do not put the engine under too much load or rev it to hard when the engine is cold as the 20 grade is a bit "thicker" than the 10 grade that it should be running on.

It is very good practice to treat an engine this way regardless of the oil you've got in it.

Bare in mind that water temperature has very little do do with the real temp that your engine is running at. Its oil temp that counts. If you do not have an oil temp gauge take it easy for 5 to 10 miles in summer and double that in winter. You don't need to drive like "Mrs Daisy" just not like Damon Hill (or whoever is in F1 these days!

)

Glad to hear that the noise has gone. As your motor has done quite a few miles your bearings are probably a bit loose so the thicker oil might be what it needs. (Other than a rebuild

)

Regards,

Pete

Post by **katanaman** » Mon Apr 23, 2007 4:47 pm

wait and see what happens when it gets oil gets older and thinner, it might return. Hopefully its ok though.

ihatesissycars · Post by **ihatesissycars** » Mon Apr 23, 2007 9:52 pm

badger wrote:HI katanaman, have a look at the manuals for pre and post serpentine engines, there's a fair difference on the clearance for the main bearings.

What are the clearances for both?

Post by **katanaman** » Mon Apr 23, 2007 10:44 pm

according to the LR manual

3.5, 3.9, 4.2 and suffix B 3.9 which is interim engine

Main bearings
Main bearing diametrical clearance 0.010 to 0.048 mm .............. 0.0004 to 0.002 in
Undersizes 0.254, 0.508 mm ................................ 0.01, 0.02 in
Big-end bearings
Big-end bearing diametrical clearance 0.015 to 0.055 mm ........... 0.0006 to 0.0021 in
Undersizes 0.254, 0.508 mm ................................ 0.01, 0.02 in
Endfloat on journal 0.15 to 0.36 mm ........................... 0.006 to 0.01 in

4.0 and 4.6

Main bearings
Main bearing diametrical clearance 0.010 to 0.048 mm .............. 0.0004 to 0.002 in
Oversizes 0.254, 0.508 mm ................................ 0.01, 0.02 in
Big-end bearings
Big-end bearing diametrical clearance 0.015 to 0.055 mm ........... 0.0006 to 0.0021 in
Oversizes 0.254, 0.508 mm ................................ 0.01, 0.02 in
End-float on journal 0.15 to 0.36 mm .......................... 0.006 to 0.01 in

This is a straight copy and paste out the RAVE manual including the fact they say oversize in one and undersize on the other. They look the same to me. The bearings are a different size but the clearances are the same.