VVC correct oil grade?

[john milner]

This has been covered many times but the answers are never clear.

All my oil changes have so far been using 5W40 or 5W50 fully synthetic (not the posh ester stuff). Rover/MG recommend 10W40 for a VVC but Caterham do not. I have now done over 60,000 miles so I assume that there may have been some wear by now. No track days just normal road usage.

Any thoughts on 5W or 10W being best for my next change?

[revilla]

10W40 semi synthetic for the VVC, 5W50 fully synthetic for other Ks. The VVC uses the oil to drive the VVC hydraulics; it measures the oil temperature and calculates from this the viscosity and the time it will take the hydraulics to move so it can anticipate. The temperature to viscosity map used is based on 10W40. Fully synthetic oils don't do the VVC mechanisms any favours, leading the wear in the sliding blocks.

[john milner]

I get that 10W might be best for the VVC mechanics to operate in tune but why semi over full? Could this just be a throwback to 10W40 being impossible to buy when the spec was written

?

[revilla]

I did try mine on fully synth. You could hear the difference. The VVC drive units became a lot more chattery. I switched back to a semi synth and it sounded a lot happier. Reading around Rover forums and the like, other people reported finding the same and there are many anecdotal reports of rapid wear of the VVC drive units on fully synth. I can't really explain why but I've run it on Magnatec 10W40 Semi Synth ever since.

[john milner]

Very odd that semi would be better than full especially as most full is not truly full. I thought the key difference would be full being harder to break down. I have been looking at Magnatec mainly because of the claims to be in place for a cold start. Edge 10W60 full is another that looks good due to the temperature it can take. The Castrol oil finder for a MGZR 160 has 5W30 or 10W60. I don't think I have seen any retailer favouring semi 10W40 only forums and Rover.

[Mechanical Moz]

Is there a Rover recommended ACEA spec for the VVC?

 

Edit: a quick Google suggests A2 from posts on MGF forums.

[john milner]

The MGTF manual says A2 or A3 is suitable and clearly states that A1 is unsuitable for VVC. 5W50 has the best range of temperatures with no mention of full/semi synthetic. For UK temperatures a 10 or 5 should be okay but 15 or above is too thick as only suitable above freezing point.

In theory this means a synthetic 5W50 should be best but there is plenty of anecdotal evidence to say semi 10W40 is best and that synthetic 5W50 is positively bad. The Caterham recommended performance grade is 5W50.

 

[mudguard]

Caterham have just put "motorsport oil 5W50" in my VVC during a routine service. According to caterhamparts it's fully synth. The car's still under warranty so I (perhaps bravely!) assume they know what they're doing....

Sounds good - noticeably better than the old oil, which I think was the same type. It's always chattered a bit but I thought TADTS. 

[SM25T]

I think they do that in all k-series. The info we picked up was that the VVC mechanism was calibrated with 10W-40 semi synthetic. I used 5W-50 for years before seeing this info.

[john milner]

In the end I could not get my head around how a semi 10 could be better than a 5 full. My change in the end was to Magnatec full 5/40 or 50. I have read about VVCs being designed around 10/40 oil pressure but even if correct the difference must be marginal.

Powertrain are probably the original source of the anti 5 full advice but I can't find a copy of what they actually said. It is possible their advice was based on what oils were readily available 25 years ago as the MGTF service manual suggests 5/50 is best.