Section : Oil and Filters

Which oil to use

Posted By : Roger Owen, 19-Sep-2005, 09:21pm

I went to my local car shop to get some EP90 for my Spitfire MkII recon gearbox (actually a 1500 type), J type overdrive and (original 4.11:1 diff) - only to find a range of gear oils with differing GL specifications. Does anyone know which is most suitable? And, will I need a different oil for gearbox and diff?

Thanks,

Roger Owen

Followups :

Which oil to use

Posted By : Aidan Cunnane, 19-Sep-2005, 09:43pm

There's some debate over this, but GL4 spec is fine (Castrol make an 80-90 EP gear oil which suits). Some GL5 spec oils are said to contain additives that damage bronze bushings and are probably best avoided in older cars. Castrol say that their GL5 spec oil doesn't do this but it may not be true for all manufacturers. You need to make sure that whatever brand you put into the gearbox doesn't have any anti-friction additives as they'll damage the overdrive.

Same oil will do both as long as you bear the above in mind.

Aidan
- Which oil to use
  
  Posted By : Roger Owen, 19-Sep-2005, 10:02pm
  
  Thanks Aidan,
  
  That's a great help, I'll stick to GL4 Spec.
  
  Cheers,
  
  Roger Owen
  - Which oil to use
    
    Posted By : Peter Bainbridge-Clayton, 18-Apr-2006, 01:57pm
    
    Okay - so let's pretend that yesterday I refilled my 1500's gearbox and overdrive with Castrol EPX 80W90 GL5........ Should I be draining this off sharpish and replacing with GL4??
    
    According to another website, GL5 is okay for the gearbox but not the overdrive...
    
    Any advice freely taken!
    
    Cheers
    
    Pete
    - Which oil to use
      
      Posted By : Ian Walker, 11-Jun-2006, 11:03pm
      
      Hi Peter,
      
      I've just had my diff refilled after having the pinion seal replaced, and mentioned this to my local mechanic who replaced it. He ordered in some GL4 oil based on previous advice that GL5 attacks 'yellow metals' (copper etc.) due to the additives in it. After he'd done the work, he checked with his suppliers - Millers (a well known oil wholesaler) - and they say that modern GL5 is now o.k. to use in diffs as the additives have been changed an no longer attack the 'yellow metals'.
      
      Not sure about overdrives, but I'd imagine the same applies. If you're still nervous, then GL4 is still readily available.
      
      Cheers,
      Ian.