wylie1

hi just wondering which oil u would advice i use in a 94 wrx will be used weekends for fun so some enthusiastic driving ive been told different oils from different people so what would be best thanks danny

scooby L

5w50 sounds a bit thin for an old Impreza... I'd stick to 10w40 out of the two

winker

iTrader: (1)

yes i agree with wylie i have a 96 sti 10/40 is the better oil.

ALi-B

iTrader: (1)

Please try and fully understand how the viscosity system works.

5w-50 is THICKER than 10w-40 at engine operating temperature. 50 is thicker than 40 when hot.

The W bit is its cold vicosity at sub zero temperatures. 5w is thinner than 10w, but that is at sub zero temperature of which BOTH oils are 1000s of times thicker than their hot viscosity.

5w-50 will also without doubt be a fully synthetic oil, due to its wide viscosity range. Most 10w-40s on the shelf are typically semi-synthetic (with the exception of a few premium or race brands, eg Motul ).

Having said that, even though 10w-40 is typically lower quality (due to most being semi-synthetic), it is perferctly adequate for the job so long as its changed regulary (6 months max for a classic shape Impreza). My preference is to use a cheaper oil and change it more often.

wylie1

ali-b so u would advice 5w 50 yes?also do u change oil pependent on milege u do or every 3 months etc?i no people say every 3 months but every one will do different milege in that 3 months so what would u advice?

scooby L

Sorry Ali..my understanding had always been the 5w was the viscosity at working temp, and the 50 was when cold.

I stand corrected

ALi-B

iTrader: (1)

As you say its how you drive the car. Generaly I equate 1000 miles to one month, so do it whichever comes first. Typically I find the cars that don't do the mileage are the ones that suffer more. Probably due to people thinking "oh, I only do a few hundred miles a month, I won't bother changing the oil", where cars that do 1000miles a month generally do it stuck at 70-80mph on the motorway most of the time, which is quite easy going on engines.

What needs more frequent changes? I'd say: If the car sees lots of short journeys (sub 30mins) or hard use or is heaviliy modified (100+ extra bhp and driven as such), Change it every three months or 3K...OR use a better quality fully synthetic oil: 5w-40 for short jorneys and 5w-50 or 10w-50 for hard use (or a fully synthetic 10w-40, if you can find one, the only one I know of is Motus 300v chrono - most other fully synth 10w-40 oils are diesel oils).

If its normal commuting (couple of short journeys, and a few 30+ min drives every week and the odd short blast or two) then a 10w-40 semi synth oil should stay good for 6months (pretty much any mainstream 10w-40 brand; Magnatec, Helix).

No worries, there are a few websites out there that also have it wrong. I recently had a customer flyer from Forté additives that also had it incorrect (it implied 0w oil poured like water at sub zero temps, when its nothing of the sort...its like treacle when cold...just like other grades oils are, just slightly less so).