Just got through cleaning the Wagon rear differential and housing, going back together with new axle seals and bearings. Thinking this might be time to take advantage in technology advancements and pick up an extra freebie in the mileage dept. I'm just a little leery that I may create a pinion seal leak. Is there enough gains from the synthetic to warrant the extra expense? I will be towing the Fly and our vintage travel trailer. It's a 10 bolt Chevy rear end, non posi .