Synthetic and conventional lubricants

This is a general question every vehicle but I would like the clever folks here to see it.

I have heard that Synthetic oils and conventional oils are compatible with each other.

What does this mean?
- Can I add one litre of conventional to top up Synthetic and Vice Versa?
- Can I use 1/2 and 1/2?
- Can I swap every oil change?
- If I drain my conventional transmission fluid knowing that I will only get half out can I fill it with Synthetic? Will there be a benefit to 1/2 Synthetic and 1/2 Conventional? ( I am specifically asking about a Mercon type here and not Mercon V).

Not including the trans but I have mixed and swaped out synthetic with regular many times with know adverse effects but have notice better running off synthetic and fuel miles.The only reason is because synthetics are so popular that sometimes I can't find it"sold out"and if other places have it there. They want to much for it. I like to shop around but if i can't get it at the right price I will mix a little whats lift over with the same brand mobil regular with mobil synthetic. Keep in mind other brands use other additives so i like to stick with the same brand at least.Just part learned and part preference. Gary.

The synthetic fluids that I use state that they are compatible with conventional.....Mobil 1 oil, and transmission fluid (my '96 calls for Mercon....not Mercon V).

I prefer synthetic fluids.....and have Mobil 1 for my engine oil (5W-30), and tranny fluid (Mercon).
I have Redline Power Steering Fluid, which lists the FORD specification number that is listed in my owner's manual.

You are FAR better to top off your synthetic fluid with conventional, or vice versa......than to run with it low......

The reason I was asking is that I plan to change the tranny fluid on a Mercon type vehicle (not Mercon V which I think is synthetic to begin with).

The factory filled this with conventional and since when I change it I will only change half I wanted to know the effects of filling it with Synthetic such that the mixture will be 1/2 and 1/2 (hmm need coffee) until the next change.

I use synthetic everywhere on '99 ... even power steering.

When my tranny went belly-up 70k miles ago, I refilled repaired tranny with Mobil ATF. At the time I just assumed this fluid would eventually be Mercon V "certified".... of course, it never has and never will be Mercon V compatable.

So my tranny is full of the wrong fluid. And I use the vehicle for towing. I try to change fluid and filter regularly, but realize there is no way I'm going to get fulll life out of tranny. So far, the tranny has performed perfectly after the repairs.

Knock on wood!

The Mobil 1 fluid has worked very well in my '96.
If you disconnect the hose in the line that comes back to the tranny from the BOTTOM connector on the radiator cooler, (bottom on tranny also), put the end that is still connected to the radiator cooler into a container..... You can then start the engine, and let it idle......the fluid will be pumped out into the container..... It comes out fairly slow, at idle, so you have time to shut off the engine. When the fluid flow slows, or starts to show bubbles, you want to turn the engine off.....measure the amount of fluid that came out.....and you then add that same amount back in of your new fluid. You can also drop the pan and wipe it out.....change the filter......before you add the new fluid back in. Anyhow......I do the drain and refill a few times......and that should change most of the old fluid out. The total capacity is 12.25 quarts.......so I would run at least 15 quarts through. By measuring the amount of fluid that you drain out each time.....and adding the same amount back in......you should end up really close on the correct level when you are done.

Im doing a little research on redline ATF it said it can be used with all types of transmissions and exceeds all Fords specs. But WOW the price tag.. For mercon V users it will be redline High temp ATF. Or the D4 ATF. I would like to go this route.

Interesting ponder now. Is the difference between Mercon and Mercon V temperature range or as I think many of us always believed it was either lubrication or hydrolyc properties?.

Mercon and Mercon V have different frictional properties....which is why they are not interchangable. I have read that Mercon V is synthetic.
Mercon can be bought in conventional or synthetic form.

Yes, Red Line is made so that it can mix with other fluids, so if you can't
get all of the old fluid out, you will still be fine to add Red Line. After
one or two changes, all the old fluid should be gone, and you will be
running completely Red Line.

Leah Wright
Technical Sales Director
247-parts.com
gary@247-parts.com <mailto:gary@247-parts.com>
1-866-88-SPEED

I was researching as you all know and this is from the source itself. This goes for most all of there products but the question i asked was for the tranny fluid. Gary
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