Oil for GT35R turbo

[g8tors]

I recently purchased a sick '05 WRX STi from the original owner. He recommends 10W 30 over the manufacturer's recommended 5W 30. I'm curious as to what's being used by other owners and why the 10W would be better. It has a GT35R turbo kit in it now along with several other mods. I live in Tampa Florida so the weather shouldn't be much of a factor. My mechanic said factory recommendations are for a reason.....
I appreciate the input from the tried and true owners of this stellar vehicle.

[EJ257]

Stock motor or built?

[MainFrame]

On a built motor I would run 10-40 or 15-40, depending on the bearing clearences and oil pump mods of course. 5W-30 is going to sheer faster than 10W-30, but 30 weight oil is still pretty thin.



If I remember correctly, it says to run 10W-30 in the owner's manual, depending on your climate. 10W-30 is no thicker than 5W-30 when the oil is warm, the only difference will be on cold start.

[Donkey]

??What oil should I use??

That being said I would run 10w-40. The factory recommended oil is pretty much for best fuel mileage,not always the best protection.

[Heide264]

My mechanic said factory recommendations are for a reason.....

Also, factory recommendations are for a factory motor .

I would bet if that has a 35R in it, (or at least hope) the motor isn't a stock motor. To my understanding, motor builders normally recommend oil choices based off of various engine tolerances and their own preferences. I would find out more about the engine in the car and ask that manufacturer. Or ask the previous owner if that is where he got his recommendation.

[g8tors]

I recently purchased a sick '05 WRX STi from the original owner. He recommends 10W 30 over the manufacturer's recommended 5W 30. I'm curious as to what's being used by other owners and why the 10W would be better. It has a GT35R turbo kit in it now along with several other mods. I live in Tampa Florida so the weather shouldn't be much of a factor. My mechanic said factory recommendations are for a reason.....
I appreciate the input from the tried and true owners of this stellar vehicle.

The motor has not been rebuilt. It has several modifications, some of which are listed below:
Ultimate Racing GT35R turbo kit
.82AR Tial 44mm waste gate
Ultimate Racing 900cc injectors and fuel rails
Walbro 255hl/hr fuel pump in tank
GT-Spec gen II header, 3 bolt flange
JIC SS/Ti 3.2" exhaust - no cats
HKS ssq blow of valve
Dyno tuned at Topspeed in Atlanta to run up to 22lbs of boost - Ecutek software for tuning

I also researched different forums reference the oil filters and someone had taken 5 different ones, measured the overall area of flow and quality of build. The Mobil 1 filter was total garbage (his words not mine) with half the area of coverage and of poor quality. After seeing the oil from this one, changed 2456 miles ago.... I would have to agree. The filter pulled off was a Mobil 1 filter and the oil was black and slightly clumpy. I added Mobil GT1 full synthetic and a Napa gold filter. I'll change it again in 1000-1500 miles to make sure whatever else breaks loose gets captured in the filter and changed.

[MainFrame]

I hope you're saving up for a $4000-$8000 motor build in the near future.

[g8tors]

I recently purchased a sick '05 WRX STi from the original owner. He recommends 10W 30 over the manufacturer's recommended 5W 30. I'm curious as to what's being used by other owners and why the 10W would be better. It has a GT35R turbo kit in it now along with several other mods. I live in Tampa Florida so the weather shouldn't be much of a factor. My mechanic said factory recommendations are for a reason.....
I appreciate the input from the tried and true owners of this stellar vehicle.

The motor has not been rebuilt. It has several modifications, some of which are listed below:
Ultimate Racing GT35R turbo kit
.82AR Tial 44mm waste gate
Ultimate Racing 900cc injectors and fuel rails
Walbro 255hl/hr fuel pump in tank
GT-Spec gen II header, 3 bolt flange
JIC SS/Ti 3.2" exhaust - no cats
HKS ssq blow of valve
Dyno tuned at Topspeed in Atlanta to run up to 22lbs of boost - Ecutek software for tuning

I also researched different forums reference the oil filters and someone had taken 5 different ones, measured the overall area of flow and quality of build. The Mobil 1 filter was total garbage (his words not mine) with half the area of coverage and of poor quality. After seeing the oil from this one, changed 2456 miles ago.... I would have to agree. The filter pulled off was a Mobil 1 filter and the oil was black and slightly clumpy. I added Mobil GT1 full synthetic and a Napa gold filter. I'll change it again in 100-1500 miles to make sure whatever else breaks loose gets captured in the filter and changed.

[g8tors]

...........1000-1500 miles

[g8tors]

I recently purchased a sick '05 WRX STi from the original owner. He recommends 10W 30 over the manufacturer's recommended 5W 30. I'm curious as to what's being used by other owners and why the 10W would be better. It has a GT35R turbo kit in it now along with several other mods. I live in Tampa Florida so the weather shouldn't be much of a factor. My mechanic said factory recommendations are for a reason.....
I appreciate the input from the tried and true owners of this stellar vehicle.

[g8tors]

I really appreciate the input. The motor will see a rebuild when I have the 4 grand or so to do it. The tuning at Topspeed to run up to 22lbs of boost has worked beautifully from the 15k mark. It just turned 62k and pulls as hard as ever. Building the bottom end and getting the heads reworked are definitely in the future

[Heide264]

Top speed seems to be a great shop. Haven't dealt with them directly, but everything I have seen from them is top notch. Their short block seems to do very well reliability wise as well.

Good shop