Mixing engine oils

[Speedy88]

Money saver in me decided to mix half a bottle of carlube 10w40 with hellfrauds 10w40. Both are semi-synth and I've had no problems doing this with just topping up. But this was a full oil change. Now in my mind this all seems fine but the paranoid part of me thinks the engine is slightly louder than normal.

Have I done a bad thing? Google search reveals that nobody really knows what they're talking about.

[trabitom99]

I personally wouldn't worry at all. Mixing two fresh engine oils is still better than leaving 2 year old, watery, sooty stuff in.

Change it again in Autumn, and enjoy the car

Tom

[Speedy88]

Cool. Will do. I shot flames out the exhaust yesterday I'll try and get it on film sometime.

[CBA]

I've been doing it for years, never had a problem. I use motorbike oil (rock oil) because it is a fiver a litre at my local parts shop and is formulated for thrashing. I also put STP in there religiously. My oil service therefore costs £11 every 5000 miles ish - I do a lot of motorway so like the high temp motorbike oil, I do a lot of booting round town too so like the 120LBS/Cm2 shear pressure of the STP - works for me.

I wont drive a car I own without STP, they're just so much quieter with it. And the power you lose with the thicker viscosity you get back AT LEAST with the extra compression.

-- STP oil stabiliser is very good for the accelerator cam too, very smooth operation and there's always some left in the bottle, never throw away an "empty" bottle of STP, you can lubricate Tectonic fault lines with that stuff.