gt4 st205 what grade of engine engine oil are you guys recommending please

>
5W-30
You could run a 10W-40 in the summer.
Synthetic Blend or conventional are ok, but I wouldnt suggest full synthetic unless your engine has been getting it for a while. 15-20 year old seals and gaskets dont like to switch from conventional to full synthetic.

Switching is an old wives tail, you need an oil which can withstand the thermal stresses of being run through a turbo charger, you need a good synthetic. I'd run 5w-40 full synth from Castrol or Mobil, whichever you prefer. You have more high quality oil options over there in the UK than we do here and 5W-40 is more readily available as it's more common for European cars like BMW's and Mercedes.

I just switched to full synthetic 5w-20 and an oil leak started that wasn't there before (or was very minimal). Before that I was running 10w-30 to break in the new engine that I finished building last year (switched at about 3k miles). I'm with Bitter, use synthetic for your car since it is turbo charged. Synthetic is very good at holding its viscosity under high heat conditions (like that generated from running through a turbo).

when the engine is new, you should just use reg mineral oil because you got to throw it out twice the first 1000 miles and go full synthetic. if you wanna go nuts diesel oils have more detergents in them but I don't know what would happen if you mix half diesel synth half reg synth

>
Leak was there, thinner oil leaks more easily.

>

lol..thanks, but not necessarily true. it depends on how small the gap is that it is leaking from. It may not have been small enough for 10w30 to get through but 5w20 does perfectly when warm, which is why I said "or was very minimal"

You just explained what I said and agreed with me, thanks.

>

lol..kinda but not really

I use 5w40 motul 300v for my car.

This post has been edited by Red123: Mar 8, 2014 - 3:28 PM

>
Oh really? I guess it was just coincidence that I blew 3 gaskets within a week of switching to Royal Purple Full Synthetic.
My 94 GT started leaking out of the oil cooler, rear main seal and oil pump gasket.

if you blew 3 head gaskets your head is warped.

>
You should probably reread my statement. Unlike the gaskets I did blow, which are subjected to moving parts and or oil pressure, the head gasket I DIDNT blow doesnt involve moving components or oil pressure. Therefore, It wouldnt make sense to suggest oil type causes a head gasket failure

This post has been edited by Special_Edy: Mar 8, 2014 - 7:15 PM

The oil didn't CAUSE the failure, they were going to fail regardless and likely had been seeping for a long time. Synthetic oils have a much more uniform and often smaller molecular structure than conventional oils so any weak gaskets or seals that were just barely holding back conventional oil WILL leak synthetic oil but synthetic oil isn't the cause of the failure. Odds are good that those seals and gaskets were going to start leaking conventional oil pretty soon regardless of what oil you used.

http://auto.howstuffworks.com/switch-to-synthetic-oil1.htm this isn't the most technical of articles but it's full of truth for the most part.

I would accept that answer for the rear main seal, but the oil pump and oil cooler were catastrophic failures. I understand that synthetic oil has a lower viscosity at low temperatures when compared to an equivalent conventional oil but this was 10W-40 which I run in the summer, versus the 5W-30 I run in the winter.

By stating that synthetic oil may cause leaks to become more apparent or worse you are conceding to my original statement that synthetics may cause leaks on a 15-20 year old motor that has never had synthetic in it, if the lazy PO's even bothered to change the oil. The odds are just greater. Period.

Oil pump seals are always catastrophic failures, same for oil cooler seals. They're under pressure, when they let go they really gush a whole lot of oil very quickly. It's a 15+yr old car, so pretty much shame on you for never having changed the oil pump seal as they're KNOWN to be a problem with the 5S, same for the oil cooler seal as well. Blaming synthetic oil for lack of maintenance is like blaming Smith and Wesson for killing people.

>
Shame on me for never having changed the oil pump seal on the car I paid $300 for.
If I had the oil pump off I would have replaced the gasket, but like the other 99.9% of celica owners I didnt replace every nut and bolt on the car just because. If I was that concerned I would have replaced the entire engine, not torn the whole timing assembly off to change one little gasket. Perhaps the most relevant bit of information here is whether or not the OP has recently changed every single gasket on his engine that touches oil. If not, shame on him according to you and dont use synthetic oil according to me. If he has changed every single gasket, then we both agree he can go ahead and use synthetic oil if he wishes.

If you reread my posts you will see that I already stated the oil pump and oil cooler gaskets are under pressure. So you have just invalidated your earlier arguement that the leaks were already there but got worse from the synthetic(also if the leaks were present, synthetic oil would instantaneously worsen the leak, not suddenly start gushing oil a week later).

Unless you have proof that can contribute to the arguement you are just making guesses and conjectures. Another member and I have stated that we first hand have experienced gasket failures following a switch to synthetic from conventional. Its up to the OP if he wants to accept your opinions or our facts.