NB Oil and fluids

Technical Area Routine Servicing
1
  1. My model of MX-5 is: NB 1.8 non VVT. 5 Speed. 68000miles

I had a job trying to figure which fluids to put in my NB. Information is contradictory. So I thought I would relate my experiences.

There was no service history on my new purchase NB so I am.part way through replacing all the fluids.

I had some 10w-40 Semi syth engine oil handy, so used that as a flush, plenty of miles done with it, motorway and urban. The engine stuttered at junctions, especially when cold, revs dropping down to 6-700 before the ecu could compensate. Happy that was only a flush.

I replaced that oil after 2 weeks with Valvoline Syn Power 5w-30 fully synthetic. The engine seems much happier now. Also put a GoldPlug magnetic sump plug in there, the origimal plug did not seem to be magnetic.

For the gearbox I used Halfords MVMTF 75W90. I used 2x 1L bottles. That did not overflow from the filler hole, so I do need to top that up. I have not yet changed the oil at the top in the cabin, I think I need to do that on this model. Less than 2L came out when I drained the gearbox, but the oil looked ok. To fill the gearbox, I used a funnel on the end of a short piece of garden hose threaded through the engine bay and into the filler hole. Worked a treat. No mess, very easy. PTFE on the filler hole plug, I think it is a threaded taper, so not too tight.

I see no appreciable difference in the gear change. Still a little notchy 1-2nd when cold. Otherwise OK.

For the diff I have Mobil Mobilube 1 SHC 75W90 Fully Synthetic ready to go in, but I am struggling to get the car level enough to do the job. Tried and failed twice. The oil just pours out of the fill hole, maybe it was overfilled previously. Will try again.

For the coolant , I have Halfords G30 AF ready to go in. What a nightmare trying to figure what should be put in, many, many different opinions. I chose this after a lot of reading. Will flush fully before putting the new coolant in.

Dot 4 for the clutch fluid. The original fluid was a pea soup greengoop. Yuk.

Not done brakes, but that will also be dot4 I think.

Power steering fluid? Dunno yet.

2

For notchy changes what condition is the gear stick gator in ? If perished replace it. Also there is a nylon bush on the bottom of the gear stick, might be worth replacing that too. I used another nylon one on my six speed and that did the trick, some people prefer to use a brass replacement bush :crossed_fingers:

3

I have not taken the top section apart yet, so unknown condition. I am expecting to have to replace parts though, 25 yrs old an’all. Shifting is fine after 5 mins or so, so not urgent.

1 Like
4

Why don’t you drain the diff first, you’ve already loosened the fill plug?

As with the NC ND, GL4 spec oil for the gearbox, 75w 90.

ATF (auto transmission fluid) oil is the stuff for the power steering

The top and bottom turret gaitors usually perish after a few years. The smaller one at the bottom when gone gives a slack feel to the gear selection.

1 Like