IainT

Can anybody tell me if it's worth putting fully synthetic oil in the scooby over semi synthetic? The car will be doing 4 miles each way to work, plus longer journeys at weekends, evenings, lunchtimes !!!
Dealer uses helix plus (semi) and Helix Ultra (fully).
Cheers
Iain.

chrisp

I thought that fully syn was too thin for the impreza. Mobil do a special 10W 40, I think. I always have mine done at the dealers and they use Shell helix which is Subarus approved oil. If the full syn helix is approved then it might be worth it espscially if you are doing short runs. I use to run Mobil One in my 24V probe as I did a town journey of 4 miles to work.

Cheers

chrisp

[This message has been edited by chrisp (edited 19-02-2000).]

johnfelstead

dont know about the scoob, but mobil1 is too thin for a cossie. I used castrol RS 10/60 on the cossie, great for uprated engines.

whether this is ok on the scoob i dont know.

HunterB

Use fully synthetic, but not Mobil 1 regular (as others have said, it's too thin in the summer and SUK have even put out a note to dealers warning not to use it). Mobil 1 Motorsport (15W/40), Shell Super Helix (as recommended by SUK) or Castrol Magnatec are all fine as long as you use at least a 10W and preferably a 15W grade. If you're only doing a small mileage each day, it's even more important to use the best oil and to change it more often.

IainT

Cheers for the replies.
I guess an extra £20 for better oil is a small price compared with the cost of the car and the job it does.

zoog

I`m most perturbed by this "too thin" business.

If you believe the Mobil 1 hype its the best oil period, no warnings about it being too thin for certain applications.
I assumed it would be just the job for turbo engines.
Can anyone explain why being thin is bad for the engine- I`m no engineer but I`d have thought it would at least spread rapidly on start up which is the highest wear point on a n engine run.
Thanks, Adrian

johnfelstead

Hi adrian,

In order to make sure all parts of the engine recieve oil from the oil pump there needs to be a certain level of resistance to the flow of the oil out of the sides of the bearings as they recieve this oil.

If the oil is too thin it will spill out of the sides of the first bearings to be fed and will never reach the components at the end of the oil ways.

It is the same effect of having a badly worn engine where the clearances on the bearings are too high.

Symptoms of this problem are a low oil pressure reading.

This is why old engines are better running on high viscosity oil, to effectively close the gaps that have developed by using thicker oil.

When i build new race engines i always use plastiguage on all the bearings during dry assembly to check the clearances are spot on.

Too thick an oil has the opposite effect where the flow rate to the bearings is too low and you get the last bearings being starved of fresh oil, this usually leads to the oil burning in the last fed bearing, this then leads to bearing pickup and eventual failure.

On some very high powered V8's which generate masive loading on the main and big end bearings i would run an external oil feed to the back of the engine and fit an aeroquip fitting in the far end of the oilway. I then feed this with oil from the output of the pump so the mains and big end bearings are fed from both ends of the oilway, increasing the flow to the bearings that could be otherwise starved.

Hope this explains why thin oil is very bad news, if it doesn't get to the bearing in the first place it doesn't matter how brilliant it is.

cheers
john

zoog

Thanks John!

johnfelstead

standard mobil 1 is no good in a turbo motor when being thrashed, it is only 5/40

mobil 1 motorsport is better at 15/50

if you want the ultimate protection use castrol RS 15/60 or motul competition oil.

aziz

Talk about a long standing issue....

This Mobil debate shall go on for ever....

U.K. Summer season ?!

Well Gentlmen it reaches 50+ C in this part
of the world and Mobil-1 15w/50 is doing
a great job......


SO THERE.....
( 99 IMPREZA TURBO 4DR.)

Ray T

I've used mobil 1 since its early days 1983/84,
it saved my mk1 astra sr from a major sieze, story was driving back from luxemburg to ostend (210 miles, 3 hours dead), it was only when i got to ostend that i realised that my water pump had blown a seal i.e. absolutly no engine coolant, if it had'nt been for the mobil's superior flow and high temperature qualities, it would have been a very expensive weekend away, as it was a new water pump was all that was needed, no other problems at all considering a 70mph average!!

also i use the latest incarnation of mobile 1 in my 1986 79k miles astra gte , the oil pressure has never dropped (the cars been on mobil since i got it in 1989.

i think i would use it in my new my00 when the time comes, you need every ounce (showing my age) of high flow cooling, especialy for the turbo bearings much less chance of the dreaded coking of the turbo oilways.

ray t

Mark Underwood

Helix Plus or Helix Ultra?

Do you want at sensible prices? Email me with your quantities and requiremnets for SIDC special prices.

How? cos I can avoid the usual wholesale/dealer mark up and get supplies direct from Shell.