I am working to repair a leak in my differential, and will need to replace the old gear oil in my 1998 Ford F150. Ford suggests 100% synthetic 75W140 gear oil, and I was wondering if that is really necessary. Will a “synthetic blend” get the job done without harming any gears? THANKS!!!
You probably can, but who knows? I suspect the reason for the 100% synthetic product is to get a broad viscosity range which may provide a slight improvement in mileage, especially in the winter time. More and more, we see cheaper made parts being protected by expensive, trick, lubricants. The oil is cheaper than making a quality part. Polishing and hardening precision gears is an expensive process. If you can take short-cuts and cover it up with a trick lubricant, well you get the picture…
Come on. How often do you need to replace it and what is the cost difference. The good stuff will last longer and provide slightly better mileage. Don’t expect to see the difference in mileage, but over the life of the fill, it likely will more than pay for the difference in cost now.
You might do this every 30,000 to 60,000 miles. Spring for the good stuff, especially if you plan to keep your pick-up for a while.
Don’t be a cheapskate! Get the full synthetic oil. Would you rather pay for a new differential?