The Camaro Club (UK)

Boring question - I've been using Mobil1 5w30 for the last year, and I've had the usual blue puff at start up.
Couldn't get my valve stem seals done - not having a head gasket set, the garage tried pressurising the bores but the valves weren't holding the seal well enough to enable them to do the swap.
My mechanic recommended moving to a thicker oil, as it might cure the smoke at start up until I can get the valves ground etc. to seat properly.

What grades are you running? I went with a 5w30 as that what the user guide for the IROC-Z said! Made the switch to synthetic as the engine's got 66k on her, and I figured she'd be ok with it - and over the last year I've had to top her up by about 1 litre of oil.

What do you reckon? Worth sticking a semi-synth 10w40 in or am I likely to damage things with the thicker grade?

My manual for the 2nd gen states anything between 10w-30 to 20w50 for an ambient 20-100degF operating temp.

You might get on better with a synthetic 10w40 and it wouldn't do any harm anyway.

I know its true of old Ford engines, not sure if applies to Chevy ones, that running fully synthetic after years of semi-synth can lead to various seals starting to leak. On a rebuilt lump its fine, but older ones do tend to start leaking. Like I say, may not apply to Chevy engines though.

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My '80 progress thread - hugger orange! Now with LQ9 power - forged pistons, LS2 rods, 236/242, .621/.612, flowed and milled 317 heads. MS3X

4L80e, 12 bolt, 4.11, Moroso brute strength posi, steel shafts.

Subframe connectors, g-braces, solid body bushes, carbon hood and front bumper, custom door cards, Autometer gauges.

It's true of any older engine with old seals. The synthetic doesn't play well with the old seals and you get them drying out and so forth, but as far as I know it's often on the higher mileage blocks. So far, after a year with synthetic, I've not noticed any drops on the garage floor, but she's used a litre over that year (about 3000 miles, I think).

Pretty sure I used to run 10-50w semi synthetic (Magnatec or something) in my old IROC... Did used to use a bit of oil occasionally.

I run fully synthetic high quality Ester based 10-40 in my 2nd gen now. It does use a tiny bit of oil, but I suspect it's more from the breather blowing it out..

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“You only live once, but if you do it right, once is enough.”

Went with the 5w30 Mobil1 synthetic in the end.
Gave her an engine flush and refilled her, and so far, I've not had any smoke at start up.