What Oil....No Not Again!!!!

I've owned my Astra 2.2 SRi since new and have always had 5w/30 put in it by Vauxhall, when I do my interim oil change I've always used Halfords GM Spec 5w/30.

I've started reading that some people use 10w/40.

What the general opinion of what oil to use. The car has 63k miles but does use about a litre every couple of thousand miles.

Gm 5/30

cheap 10/40

Having driven almost 500,000 km in my astra and having tried virtually every possible oil viscosity and brand i can confidently say this. The best by FAR is a combination of 3.5litres of full synthetic PAO 5/30 and 1 litre of 10/40 semi synthetic. Any brand will do. You will hear and feel the difference. The tricky bit is maintaining the ratio because the diff oils burn off at diff rates.

For a very long time i used full synthetic PAO 0-40 and this gives excellent fuel consumption, keeps your engine pristine in cleanliness BUT the engine took a bit longer to settle down to nice idle after a cold start and my lifters were a nit noisy on start up with that. Using the the said oil combo above seems to have solved that and the engine now quickly settles down to a nice sweet sounding idle........

Ive seem pics of inside of engines after using straight 10/40 and they looked really dirty even ones that have been changed every 5000 miles. Have a look at my head after 455,000km in preparation for its FIRST chain change

https://z22se.co.uk/threads/pics-of-my-head-after-455-000km.27158/

I find the 0w30 oil tends to burn off faster, so I try and avoid it. 5w30 or 5w40 is much better and 10w50 is more aimed at track cars.

I use 10w40 magnatec Part-Synthetic in mine, because it has ACEA A3/B4 and this is supposed to be very good.

I used to use GM 5-30 fully, but found it burnt off a tad quick, since the new engine I had fitted a few years back always ran on GM 10-40 or 10-40 Magnatec.

What do you guys think about this one:

Johnss said:

What do you guys think about this one:

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Ur engine will run fine and smooth with this but it wont rev as effortlessly and it will use more fuel and i say this thru personal experience with it. The cost saving of using semi synth 10-40 over full synth 5/30 is more than negated by increased fuel consumption. I do the same 180km round trip to work 6 days a week and in my car fuel consumption with semi synth 10/40 is 10% higher than full synth 5/30. Also this will leave varnish in your engine even with regular oil changes it wont be excessive but it will be there no question.

Using a 4:1 ratio of full synth 5/30 and semi synth 10/40 seems to give the best of both worlds. Low fuel consumption and doesnt burn off as quick as 5*30 on its own.....and for reasons i can only guess at it keeps my lifters quiet on a cold start up when either oil on its own would have them tapping........just my two cents worth........

Vectra B SRi (Z22SE engine) Without too heavy a right foot we average near 35mpg and only use GM 10W40 semi synth. I very much doubt we would/could get better than that unless we drove like nuns.

identiti66 said:

Vectra B SRi (Z22SE engine) Without too heavy a right foot we average near 35mpg and only use GM 10W40 semi synth. I very much doubt we would/could get better than that unless we drove like nuns.

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35mpg is not bad for a heavy car like the vectra - with a lighter astra and a heavy foot i do about 40mpg of mostly motorway driving (about 70%)