Engine oil change

I have a 1998 EB with 95000 miles. been following manufacturing recommendations of using 5w-30 for oil change but today a 10w-40 was used (eventhough I asked for 5w-30). I was told that 10w-40 is better because of the high mileage. Is this true, will a big change in oil type cause any problems ? Thanks for the response

what size motor do you have? if its a 4.0 sohc it will be fine , if it is a sohc i would use strictly whats recommended for the bearing tolerances...

SORRY if its not an sohc it will be fine

Thanks for the reply. It is SOHC 4.0 L, do you recommend going back to the shop and changing the oil back to 5w-30 ?

Yes I Work At A Ford Dealer..the Higher Grade Of Oil Will Make The Engine Run Warmer Plus Your Starving The Engine For Oil, Because It Cant Get To The Cams In Adequate Time The Oil Is To Thick To Go Through The Tight Spaces...

is 5w-30 the best oil or can I use 10w-30 due to the high mileage

The difference between 10w30 and 10w40 is how much viscosity improver is added to the base oil. 10 is the base viscosity of the oil, "w" indicates that it is suitable for winter use, and the 30/40 indicates the operating temperature viscosity equivalent of the oil. In other words, both oils have a lower viscosity at operating temperature than cold SAE 10w, but at operating temperature, 10w30 should have the same viscosity as SAE 30 at operating temperature and 10w40 should have the same viscosity as SAE 40 at operating temperature. SAE 10w, 10w30, and 10w40 should all have the same cold viscosity. Some argue that 10w40 has too much viscosity improver and not enough base oil to lubricate effectively. Others reason that the extra viscosity causes too much windage and decreases fuel economy. I've used 10w40 more than any other grade of oil and it hasn't caused me any problems. However, since Ford recommends 5w30 oil in the 4.0L SOHC, that is the oil I would use, since it will flow better cold. Yes, engine wear will create greater bearing clearance, but valvetrain restrictors are what dictate the correct viscosity oil in this engine.