wrong oil


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Mar 20, 2008
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Can anyone tell me if putting the wrong grade oil in an engine can cause low oil pressure. e.g putting semi in when it should have been fully synthetic. This may sound a stypid question to a lot of you but im getting desperate for answers. Thanks
When I went to Audi they told me Semi would be fine in my car if I wanted. What Grade have you used?
The garage has put 10-40 in the car but everyone i talk to says i should of had fully synth in it, its just that i dont know if this could be enough of a diffrence to cause low oil pressure because the garage wants to change the big end bearings now to be safe. The cars allready cost me hundreds last week so i dont want to spent hundreds more on something i dont have to do. Any ideas?
I's the grade, 10/40 or 20/50, that is going to affect oil pressure, not what the oil is made of.

What are the symptoms that make your mechanics want to change the big end bearings?

I would be looking for a second opinion before going further.

Read some history now. I don't see big end bearings being your problem, it would knock badly and it sounds like you only have tappet problems.

I wonder if the flush has dislodged something that has partially blocked the feed up to the head, so the tappets are now getting starved of oil.

If you post up where you are in the country, then we'll be able to advise of a local VW specialist that may have seen this problem before.

The reason they are thinking of the big end bearings is because they put a pressure test on the car and it was only on 2bar at 2000rpm, I think its suppose to be around 3.5 bar. A few peaple have said that maybe the flush was so good its got rid of something that had built up with the mileage over the years and now its gone ive lost pressure. Ive no idea whats going on, all i know is that it was fine before it had the service done. I live in Caernarfon in North wales. Thanks
It's likely the flush has dislodged sludge/crap from ****** oil over the years and it has blocked the bottom filter that takes the oil to the top end of the engine....not un common on 1.8T's......

Dont know for sure but suspect you will need to take the sump off and clean all the sludge out and replace the filter then rebuild and should be ok with any luck - had it on a Passat 1.8T....

If you want to have a chat with a VW specialist over ther phone I would suggest you give www.tuningwerkes.co.uk a call as he has had the problem on both his 1.8T's...really nice bloke as well..
Often happens when cars do very little mileage (short trips) or wrong oil is used or missed a service all together - my Passat had low mileage so short trips and had missed a serviced...doh
Hi mate, Thanks for your reply. We have had the sump off twice fitted a new oil pump, and oil pick up pipe. The sump is so clean now it looks better than new. I thought doing these things would sort it but it hasnt thats why im drawn to thinking its the wrong oil, it was fine before the service.
The main thing with semi-synth rather than fully is that you get a longer service life, shouldnt be causing trouble with pressures like that really
Cheers for your help guys, think ill just have to sit tight and see what the garage comes up with and hope its not too bad. Dont you just hate it when things go wrong, that money could of gone towards a remap, gutted.
I've not read your other posts, but my guess would be either a worn or blocked oil pump, possibly because of the engine flush, or a stuck oil presure relief valve it these engines have one (I guess they should).
If your garage are saying they think its the big end/main bearings, ask them to take a couple of the caps off so you can have a look at the bearings for yourself. If there is any scratching or if the white metal has worn away and they have orangey patches, or if your crank is scored then you need to get the crank out and checked and reground if needed, and new bearings to suit.
Hi mate, spoke to the garage earlier and they are conviced now that it is not the big end bearings. Never heard anyone else mention the oil pressure relief valve, do you know what this looks like or where it is if i have one. The garage have got some fully synthetic vw oil today so tomorrow their going to try that if that doesnt work theyr goint to disconect the vvt solonoid in case that is stuck open. The oil pump and pick up pipe have been renewed. Any more info on the o.p.r.v would be greatly appreciated, im willing to try anything.
I don't know for sure if these engines have a relief valve, but my guess is it should have one of some description some where. Get your mechanic to have a look.
Just had a call off the garage. Today they drained the oil, gave it another flush, put an air line on anything that could have blocked then filled her up with fully synthetic and a new genuine oil filter and shes like new. No warning light no tappet noise and goes like a dream. Im so glad i didnt go to more expences before trying the oil. Thanks to everyone that replyed, its much appreciated. Tony

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