Outer Limits 4x4 Board

Hi All
I've got a 94 Sierra with about 172,000km and it starting to blow a little (very little) smoke under load or high revs only.
Just wondering what weight oil would be best, i usually run 20/50 but should i go to a thicker oil?
If so, how thick? Would something like Helix Old Engine Oil be ok for such a small motor? or maybe a staight 40 or 50.
If i run too thick of oil, will that under power the engine?
I'm trying to make the motor last as long as possible, as i'd like to do a 1.6 conversion in the future.

Thanks in advance
Pep

I was using a Shell Old Engine oil in the Corolla, it was a 20w60 from memory (1.6L) and it seemed to stop the smoke a bit. Also Wynn's stop-smoke treatment works wonders...

G'day all.
I've been using Penrite oil in my '85 LWB softop for years now and swear by it. Gawd knows how many kliks the G13A engine has done, it was fitted after daughter & boyfriend cooked the original about seven years ago (I've owned the Sierra since 1987). There is also the little fact that the odometer somehow set itself back to 00000 about six months after I bought the car, so I don't have a clue how many kliks it has done!

Anyhow - I run Penrite 40W-70 in summer, just about to change to Penrite 20W-50 for winter. The 40W-70 comes out of the bottle like cold honey, it really is that thick, but it offers great protection in the heat of summer and keeps the engine running quieter - and no exhaust smoke. I got onto it through it being popular for classic motorbikes back when I was riding, before I parted company with a Yamaha 1100 sidecar outfit and stuffed up my spine! I also like the fact that it is Australian-owned and developed for our conditions.

That's my 20 cents worth, I reckon Penrite is the duck's guts for older Sierra engines.

Cheers - Longbaser.