Andy13186

I got a 2018 GT performance pack and put 1k miles on the stock oil (I drove it easy for about 350 miles then got harder on it around 500 miles and lots of full throttle after that) I may change it soon possibly. I have a ton of 5w30 Amsoil signature series left over from my prior car.

In the manual Ford does say to change to 5w30 for track usage then change back to 5w20 for street...

Is it really necessary to keep 5w20 in it for street driving even if you drive the car hard and in a hot environment? What do you guys think? Maybe the 5w20 helps the fuel economy slightly and thats why they recommend it? I dont care about fuel economy I just want my engine to survive best.

spectreman

I'm not a Ford or oil engineer or mechanic but as I understand it-
The lighter weight oil is required because the tolerances inside the engine are so tight now that the engine oil needs to be light enough to filter through. Also, today's engines reportedly suffer from greater carbon build-up than engines of the past and require the lighter weight/synthetic oils to help fight that.

Who knows if any of this is true or using something other than what the manufacturer recommends will cause long term harm.

Me? I follow factory recommendations, not anecdotal stuff from all the supposed experts found on the net. IMHO, nobody knows the engines better than the manufacturer; after all, they're the folks who designed and built them.

08'MustangDude

Yes, a lower viscosity oil like 5w20 will provide less protection than 5w30 in normal operating conditions.
However, a lower viscosity oil is better in areas of the country with lower average temperatures and below
freezing conditions. If you never see freezing temps, 5W30 is fine...
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proeagles

This is the correct answer.

08'MustangDude

I run whatever I want, and not ONE of my cars has had engine problems, and all well over
150,000 miles on every one of them. I run 5W40 in my 4.0 right now, but will be 5W30 in
the winter. I have run the **** out of three cars the last four years, all well over 160,000,
and one at 243,000 when VW bought it back. My current VW, I run 0W40 in the winter, and
5W40 in the summer. It calls for 5W30, so 5W40 should cause long term damage... Well,
I will be over 165,000 by the end of the week... Got the car with 38,000 miles on it...

Carbon is an issue because OIL CONSUMPTION rates are also high! Get a catch can, and
that will help. Carbon is also an issue for direct injected engines, since gas does not
wash over the intake valves.

5W20 is the recommended weight by the manufacturer, but 5W30 will not hurt in hot climate
areas of the country.

Oil consumption is also based on the oil, and I proved it! I ran my TDI with Rotella T6, 5W40 and
my catch can would fill up twice between oil changes. I switched to the cheaper DELO 400, another
5W40 synthetic, and it would not even be half full at the next OCI. So, you can't say a 5W20 will
have less blow-by for less carbon build up, when I went through Castrol, Rotella, then finally DELO
for less blow-by. Blow by is oil consumption, because if it's anything else then you are
burning it in the chamber, which is NOT good.

OIL stuff always starts huge opinionated posts, but I have experimented with oils, and I find the
one that works for me, and every car, as I said, well over 150,000, never, EVER have I had
an engine fail, let alone one due to oil weights.

if I were in CA, FL, AZ, and other like states, I'd run 5W30 in my 18GT, but that's me...