Gearbox Oil - MTL Redline or other?


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Looking at getting my gearbox oil changed - I've done a forum search and there's lots of threads with people using all different stuff but one that seems to crop up regularly is MTL Redline 75w-80

Looks fairly expensive compared to other oils, approx £40 for 2L.

Are there any equally good oils at a better price? Is it worth spending the £40 for Redline?

Not sure if it makes a difference, but I don't track the car.


this stuff made a difference to was about £17 a bottle when I bought mine from opie...much smoother change of gears..some like it some dont..wont know till you try happy with redline stuff
Loads of recommendations for the Redline stuff on here & from Opie Oils. I personally thought that gear changes felt slightly worse when I changed to it. I then changed to the apparently "new" Renault recommended stuff (ELF Tranself NFJ 75W-80) and it felt slightly better :001_unsure: My gearbox is still hard to get into 1st when cold and is very notchy, especially when trying to get into 2nd from 1st but no crunching or anything too ominous.

Also, change it yourself on a nice day as it's super easy :smile: there is a How To thread if you need it.


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[MENTION=2904]Jamz72[/MENTION] - don't suppose you have a link for changing the gearbox oil? I tried the one in the How To section (Guide: Change gear box oil: Clicky) but it goes to a dead end link

Was planning to ask a friendly mechanic to do the work as I'd also like him to investigate some jump/knock when coming off the accelerator/clutch in at low gears/RPM. Seem's to only happen when shifting between first and second gear when below about 3K rpm. If I keep the accelerator very slightly pressed it doesn't happen. I have a feeling it might be engine mounts or something like that, but not being very mechanically minded - could do with a second opinion.
I went with a mix of MTL and ATF in mine, 1 litre of MTL and the differnce topped up with ATF.

So far i have noticed little difference compared to the gearbox oil that was in there before, however i have only driven a few miles so its unfair to say there is categorically no difference from switching to Redline.

However, if nothing else, i have the piece of mind it has decent synthetic fluid in there for not too much outlay. Its an easy DIY job providing you have a pump to refill the box.


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[MENTION=52200]montana[/MENTION] - I've dropped [MENTION=205]oilman[/MENTION] a PM about the MTL Redline stuff, waiting for him to get back to me.

I've given my friendly mechanic a call and booked the car in for next Friday for a gearbox oil change, and also to take a look at a knock I seem to be getting (which sounds identical to the issue you're currently posting about too -

I've advised it's likely the lower torque mount causing the issue so he's going to check that out along with the clutch. If you get any further with resolving yours before next Friday, drop me a PM with any info :smile:


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[MENTION=10886]ChrisR27[/MENTION], would be great to know if something like this is as good/effective as the MTL Redline stuff, especially since it's half the price. Any idea when you'll be putting it in?
Having done a bit of reading about gearbox oil across multiple forums and some lightly technical white papers it seems like a real minefield.

From what I read gear oil classified as GL5 isn't great for brass synchromesh components, but good GL5, like Titan Syntofluid 75w80, should have the correct additives that won't kill brass. At one stage I thought GL4 would be the oil to go for. Then I noted the Elf Tranself NFJ Renault recommend is GL4+, so it meets both GL4 and GL5 in one oil. Presumably the Elf oil has the correct additives that don't kill brass.

Elf have also produced a new version of Tranself NFJ, Tranself NFP 75w80. Both are recommended for TL4 gearboxes. The NFP has slightly better characteristics. Its pour point is -51C vs. -40C for the NFJ. NFP is 12 points higher on the viscosity index. Interestingly the NFP has a lower kinematic viscosity value at 40C, 36 for the NFP and 47 for the NFJ, the values are measured on the scale of mm2 per second (of oil flow). So (I think) the NFP would be more free flowing at the start of driving. They both had the same rating of 8.5 at 100C. Although I could have interpreted this incorrectly and it's the difference between the 40C and 100C value that's most important i.e. the least variation. That would make NFJ better as 36 to 8.5 is less than 47 to 8.5.

All the spec sheets for Elf NFP and NFJ, and Titan Sintofluid and Sintopoid are available for download. I couldn't find one for the Redline. Only the Elf NFP lists a flashpoint (192C), the NFJ doesn't. It's 190C for the Titan Sintofluid.

It seems that 75w80 is definitely the viscosity to use and not to move to a 75w85. The 75w85 is quite a bit 'thicker' at high temperatures and may cause added drag, or not allow the components to engage and disengage as smoothly as a 'thinner' oil would at the same temperature.

All of this is fairly academic though. As I bet a large proportion of the gearboxes that have failed were still filled with the original Elf oil Renault put in them in Dieppe. So if they still go with Renault recommended oil in them, using a high quality synthetic like Titan Syntofluid or Redline should be fine.

Personally, I think I came to the decision I would use Elf Tranself NFJ or NFP 75w80. The values on the spec sheet for Titan Syntofluid didn't seem quite as good if I recall and it's a GL5 not GL4 or GL4+.
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[MENTION=51465]ShantiT[/MENTION] I'm looking at the Fuchs TITAN SINTOFLUID now, opieoils on ebay can get 2L to me for £21.88 which is cheaper than buying from them over the forum with 10%.

Just trying to establish if there's any worthwhile reason to pay (double) for the MTL Redline, which currently it seems there isn't.
@CallorFord I didn't know Opie had an eBay site, good to know. Especially if it's cheaper than their own website with the forum 10% off.

The big thing with the Redline MTL is that it's GL4. Not GL4+ or GL5. Redline claim it's safe for brass synchros, as it lacks the reactive sulphurs found in most GL5 oils that cause damage. They say 'most' oils. Therefore the questions must be, does the Titian Sintofluid have reactive sulphurs? As it'd say it's not 'most' oils. I highly rate Silkolene (Fuchs) and have always used ProS 5w40 in all car engines without any issues. Also, if the Titian has reactive sulphurs to meet GL5 classification, does it have additives to minimise any reaction to brass components while still meeting the GL5 classification? I'd say the less additives in an oil the better.

These were some of the reasons I decided that I'd go for Elf Tranself when the time comes, probably the NFP, as it's been 'upgraded' over NFJ and the spec sheet clearly states 'advanced protection' for synchro components. It's also GL4+ not GL5.

An advantage to the Redline and Titian could be that they are both fully synthetic. The Elf is likely to be semi-synthetic and not ester based as the Titian is likely to be. Would the benefit of an ester based fully synth' outweigh having the additives added to it to stop it eating brass? Does the Titian actually have the additives at all?

The Redline has viscosity values of 54.1 at 40C and 10.4 at 100C. A spread of 43.7 vs. 38.5 for NFP and 27.5 for NFJ, and 40.4 for Titian. The viscosity values of the Titian are 49.8 at 40C and 9.4 at 100C. Again, this is all based in the lower the spread the better. Therefore NFJ wins. Note the Redline and Titian are higher values at 100C vs. both Elf being 8.5 (a higher value at 100C means 'thicker' if I recall correctly. The pour point of the Redline is -50C, so similar to the Titian at -48C, but not quite as good at the NFP at -51, and way better that the NFJ at -40C.

I really need to look out the papers I read that drew me to the conclusion that the lower spread the better when it comes to kinematic viscosity. Then the kinematic viscosity values can be correctly interpreted. I don't know if Opie would be able to discuss how to interpret kinematic viscosity with you. They may also not know what additives the Titan has to stop reactive sulphurs eating the brass synchros, or even if it has any in it.

So, overall, Redline GL4 is isn't going to react to brass, is the correct 75w80 viscosity and (I think) fully synthetic ester based oil, but expensive. Titian is the correct 75w80 viscosity and fully synthetic ester based and cheap, but might react to brass synchros and is GL5 rated not GL4. Elf NFJ and NFP are manufacturer recommended 75w80, GL4+ and fine for brass synchros (so they claim) and cheap, but not fully synthetic.

Beyond that it's going to boil down to each oils flash points, pour points and correct interpretation of kinematic viscosity. Told you it was a minefield! ; )
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I have recently just bought this havent had a chance to put it in yet tho so can't say what it's like
Had it in mine about 5,000 miles now. Doesn't really fix the crunchies as it's more down to the way you drive, but it did help with it. Tends to start working after about 100 miles after it's mixed up a bit. I find the gear changes get smoother, but once you crunch it, it goes back to feeling ****ty. No idea if it's placebo but just my 2 pence.
Spec details for Redline here:
Spec details for Elf NFP here:
Spec details for Elf NFJ here:
Spec details for Fuchs here:

Page with all spec details for all Elf/Total automotive applications:

Technical notes from Renault re transmission and final drive oils from 2004. It recommends the Tranself and makes a big fuss about damage being caused by not using the correct lubricant. That's going to relate to quality and viscosity over brand I expect. The NFJ and NFP have likely superseded the TRT mentioned


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I've placed an order for the Fuchs TITAN SINTOFLUID - as I'm not experiencing any gearbox issues anyway, I likely wont notice much/if any change. Will try and remember to update this in a couple of weeks once it's been changed. Got a drive up to Cannock and back over the weekend so that'll see a hundred miles or so to run it in.
Anyone using Motul gear 300 75w90 for hot climate or racing use?

I am currently using it with smooth gear shifting. The w90 is great for my extremely hot climate at 33 degree or track use.
Having done some re-reading I think these are good ways to interpret the 'box oil spec sheets.

An oil that has a smaller change in kinematic viscosity with temperature will have a higher VI. The higher the VI (viscosity index) the better as this is the rate of change of viscosity between two temperatures. The lower the VI, the more the drop in viscosity as the oil warms up. The higher the VI value, the less the drop in viscosity as the oil warms up. The benefits to a higher VI oil are that not only is the oil thinner when cold, but it is thicker when warm. A higher VI oil can only be of benefit to a gearbox in a cold climate in Winter months.

On this basis the Elf NFP performs better than the NFJ and Titian which both have a VI of 175, and better than the Redline which is 185 vs. the NFP at 187.

Kinematic Viscosity is a measure of the fluids resistance to flow and shear under the forces of gravity, or how easily the oil flows to the different parts of the unit it's lubricating. Kinematic viscosity is usually quoted in data sheets at 40°C and 100°C. Kinematic Viscosity using the ASTM D445 or ISO3105 testing methods is 1 centi-Stoke (cSt) = 1 mm2/s. The ideal viscosity at a bearing point is around 10cSt or higher depending on various factors such as the load, rpm and design or dimensions of the bearing. Much higher than this and drag results, much lower than this and boundary lubrication occurs (boundary lubrication is lubrication by a liquid under conditions where the solid surfaces are so close together that appreciable contact between opposing asperities is possible).

Using an industry chart the minimum viscosity at 100C for 75w SAE is 4.1 cSt, and it has to be less than 11 cSt at 100C for 80 SAE. So the Redline with a value of 10.4 at 100C offers a good level of protection as it's above the 10cSt ideal at a bearing point, and not much higher so drag shouldn't occur. The 8.5 cSt of the NFP and NFJ is quite low, but still above the line on a commonly used viscosity/temperature logarithmic graph, meaning it's classified as an oil with a small change in viscosity (which is good). Lower than 7.75 cSt at 100C on the logarithmic graph means the oil would fall below the line to a large change in viscosity classification. The Titian is 9.4 cSt at 100C, so fine, possibly better than the NFP and NFJ at 8.5 cSt, but not offering as much 'protection' as the Redline.

Yet the VI (viscosity index) seems to be the best indicator of performance. The smaller the change in kinematic viscosity the better the VI. So back to my original interpretation that the narrower the spread the better. Which puts the NFJ in the lead, but not based on the reported VI given on the various spec sheets. Going by the reported VI the NFP wins.

All of this still doesn't consider that the uniformity of the molecules in the PAO esther synthetics will be consistent over time. Therefore the viscosity will change less compared to semi-synth, which will be subject to molecule change and change in viscosity as time passes. So considering the PAO ester based Redline, that it has the second best reported VI and it's GL4 so won't eat brass, it looks like it could be the winner...

Overall I think all this is going to be marginal and up to personal choice. The GL4 vs. GL5 sulphur creating brass eating oil has to be a factor and whether it has additives to counteract this. As has the synthetic vs. semi synthetic and price argument. Synthetic you pay more for, but don't have to change as regularly as it's maintains the viscosity over time.
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