Michael Charalambous 12 Posted February 19, 2018 hey boys just wondering what diff oil everyone recommends to suit a 9inch 4:11 full spool and are any additives required? its only a mildly worked street car. Any help would be greatly appreciated Share this post Link to post Share on other sites
gerg 10,871 Posted February 19, 2018 You really can't go wrong with a good quality full synthetic gear oil. Expensive but worth it, at about $30 a litre. Castrol Syntrax 75W90 is what we used in the Falcon one-tonners that were having diff issues. Once we started dumping the factory mineral oil and replacing with this stuff, the diffs were living a lot longer. Synthetics cool better as they seem to be thinner and flow more nicely for the same amount of protection.Sent from my CPH1607 using Tapatalk 1 Outback Jack reacted to this Share this post Link to post Share on other sites
Outback Jack 6,352 Posted February 19, 2018 Im running Penrite Full Synthetic in my 3.45 diff... runs nice.... think same-same as fully synth above.Sent from my GT-S7583T using Tapatalk Share this post Link to post Share on other sites
broken-wheel 659 Posted May 5, 2018 I'm running https://www.penriteoil.com.au/products/gear-box-oil-30 .... not sure why people run such heavy oils these days, that's like from the 60's, just run this and change it every few years, it's like 20W-60W which is ok, just give it some time to warm up and it will quiet as it warms up, I like it some of the 90W oil is just fucking stupid, if you'd be drag racing it I'd probably just run ATF and change it every few months 2 CHESTNUTXE and Slow250XC reacted to this Share this post Link to post Share on other sites