Thread: What oil?

when I was into vintage vw's a very experienced porsche mechanic and vw enthusiast used to swear by mineral oils in everything, claiming that in older vehicles the synthetics could weep through gaskets due to molecule size.

I would imagine this doesn't apply to TD5's and only to older cars with cork or paper gaskets, or maybe it's just bull!

Originally Posted by lyonsy

i have tried most of the different oils and some not recommended ie rx super 15w-40 and oil samples never came back with any difference or noticed any difference in fuel economy

but do remember that as the oil gets older and degrades the viscosity adders are what breaks down so if you run 0w40 oil it will slowly break down to a 0w straight oil tbh a 10w30 oil would be a better oil then a 5w or 0w 30 oil if you plan to do more then 10'000km on your oil and dont go where its freezing or if you do its only for a few days and give the engine 5 mins to warm up before heading off.

as for what brand what ever you can get that matches up and is the cheapest so long as its not a no name brand

dont get to concerned on synthetic vs semi vs mineral there all still made from crude unless you get some really really high end synthetics that you wouldn't put in a td5 and there is argument for running mineral oil as due to the different size molecules can give greater shear performance, where as synthetics are better at suspending particles in the oil which is why they can be used for a longer time (generally works out around the same cost for those extreme range oils vs a std mineral oil)

Yep, I've committed heresy on here a long time ago by mentioning using a 15W-40 in the TD5, but the bloke was in Darwin and doing 10,000km drains, why use a 5W-40 ?

FWIW a 15W-40 pumps ok'ish even in Canberra at -7*, you just take a few more minutes of taking it easy while the oil comes up to temp.

What tends to happen with the wide viscosity oils like 0W-40 is that they start to shear to an SAE30 oil as the VII's break down, and then thicken back towards an SAE40 oil at the end of the oil drain with oxidation.
Mobil 1 0W-40 is particularly known for this.