Clean your intercooler for better MPG!


Hello all
Recently dicovered that the air pipes to and from the intercooler were really oily inside. Wondered if my turbo was knackered but didn't show any of the classic symptoms. Anyway, realised that there is a breather from the rocker box plumbed into the intercooler air pipes so that explains the oilyness.
Anyway, recently changed the cam belt and whilst the front end was in bits I decided to clean out the intercooler. Sure enough about 100mls of oil had collected in the bottom of it. Put a load of paraffin in it and gave it a good shake over the course of a few days then thoroughly dried it in the Rayburn (being careful not to blow up the kitchen!).
Anyway, now it is all back together but the big surprise is an increase in MPG from about 28 to over 31. Maybe doesn't sound a great deal, but it is an increase of over 10% and purely down to sloshing a bit of paraffin around in your intercooler.
Nothing else has changed so it must be the cleaner intercooler helping the whole turbo charging system to work more efficiently.
Hope you find that useful


Cleaning the intercooler and its pipws are always a good thing, it gives better heat exchanging and cooler, more dense air to the engine. Many commercial vehicles doing high mileages specify this as part of their servicing schedule, and it lowers emissions slightly.


This is interesting as i have also noticed oil in the pipes leading to the turbo on my f78, i cleaned the the oil from the pipes and thought nothing more of it !
I will now remove the intercooler and investigate.
Just a thought, but the intercooler on my fourtrak appears to be quite small compared to the intercooler on my last 4x4 (Landcruiser), i have also heard landrover drivers fitting bigger intercoolers for more power.
would it be worth fitting two intercoolers or a larger one to a fourtrak ?.


Twin intercooled Fourtrak !!!!!!!!!!

Interesting comment about increasing intercooler capacity, ???

Air flowing through the intercooler will only cool to the ambient chill factor . I see what you are suggesting that the air passing through the intercooler will be as dense as possible (more oxygen )by increasing the exchange area/surface, therefore more power !!!!!!!!!!. The longer the pipework , the bigger the intercooler matrix and the Turbo has to be push the air through all this !!!, would probably need a higher capacity Turbo and a recalibrated injection pump to show any real benifit.

Just my thoughts , not an engineer, but been down these routes before.

Addition- I have spent some time looking at post's on other site's and the evidence seems not proven, as you do not find reference to the truck/engine being tested before or after on a rolling road or engine test on a dynometer, just the owners perception of a power increase, by just increasing the size of the intercooler. All the other factors from the air intake through to the exhaust must be considered !!!!

Edward (ews) '92 Fourtrak 2.8 TDX


increasing the intercooler size might do two things:

it might decrease the temperature of the air entering the cylinders, therefore increasing the density and giving more power.

it might increase the pressure drop between the turbo and the cylinders (assuming the air has to travel through a longer pipe, possibly with more turns and x-section changes) therefore decreasing the density and giving less power.

the density is directly proportional to pressure over temperature so it's really a trade-off between the two.

if the standard intercooler already does enough to decrease the temperature of the air down to close to ambient, then all you'll be doing with a larger (longer flow passage, more turns) is possibly increasing the pressure loss (as the temperature can't go below ambient!). i suppose if you got hold of a better designed intercooler you might get a decrease in pressure loss.

i don't know much about intercooler design but to really work this out the simplest way would be to measure the air temperature and pressure at intercooler entry and exit at high rpm and compare the two (or several) intercoolers to see which gives the best performance. there are more complicated methods to work it out, which are presumably those employed by high performance intercooler designers.


More Power

I was in my local favourit parts supply establisment today, they are mainly a workshop for Japanese rally cars,ect, and have a rolling road with all the goodies that comes with tuning these cars, but have a really good partsman and he do'es his best for me as a Fourtrak is not his usual fare. ( I will ask them to put the Fourtrak on the system one day, if I have the nerve !!!!!) Talking to him about increasing the turbo size, ect , he then fetched the head/chief mechanic who told me it was not uncommon for boy racer types to bring a car on which they had fitted a bigger turbo , after market waste gates , ECU chips and who where most disoluntioned when told the output of there car, lots of techy stuff which I did not understand !!!, BUT they could offer me some decals maked "Twin Intercooled" or "Twin Turbo" from a local decal outfit!!!!.

Edward (ews) '92 Fourtrak 2.8 TDX

indeed i believe turbos are

indeed i believe turbos are carefully matched to engines, i.e. it's not just a case of strapping on a 'bigger' one.

thats what i keep telling

thats what i keep telling the mrs!

Fourtrak Fieldman TDL 3" Body Lift on 31"x10.5 MT's
Chugging away nicely on B100 - happy days!!!

Reply To EWS

This is true, but when an uprated intercooler is used it must be done as part of a tried and tested package to achieve results. One sure fire way of inproving performance is to swap a host of other items, not just one item.Many of the engine tuning suppliers sell uprated intercoolers, these are usually better conducters, thus improving the thermal transfer of the passing air at ambient to the compressed air in the intercooler. These items come at a price, a significant one, and are generally exact copies of the original manufacturers fitment, although in a more exotic material. Cost is the main factor, many of these exotic material manufactured components come at often 10X the cost of an original item, and with no noticeable performance of economy are only to be fitted by those with more money than sense.

One simply way to improve performance is to remove the intercooler every year and clean it, and when you wash your vehicle, backflush the existing item with the hosepipe. This ensures the normal build up of dirt, flies, and other accumulated items are removed so its working at its optimum, its as simple as lifting the bonnet and cleaning the matrix with a hose.

One other point is not to paint intercoolers with any old paint, use only the correct thermally efficient heat transfer paint as used by professional radiator manufacturers.


In designing intercoolers, most vehicle manufacturers design them for the optimum workings of the engine, and the vehicles working conditions. In general the misconception is that fitting a larger intercooler will work, this is not the case as the manufacturers have already provided the optimum for the vehicle. This is also matched to the fuel injection system, as this will also provide the optimum fuel for the cooled air, so fitting a larger unit will often create more fuelling problems.

Fitting two units will not be viable as this will create more internal air friction, thus depriving the free flow of air to the engine. If this were a better option it would have already been done as an inter and after cooler.

Intercoolers are matched to air flow, and air requirements, and as all diesel engines receive a surplus of air anyway, whats the point of supplying the engine with an even greater surplus of air.

All in all the claims made have been disproven by me and many others, time and time again; unless there are other modifications to provide substantially more fuel to the engine, then uprating the intercooler is an expensive waste of time.