Ford Model T – Engine and Differential Oils

Model T engines do not have oil pumps.  They use a very simple splash system.  Oil from the sump is lifted to the top of the motor by the flywheel and then it drains back down.  The engine and transmission use the same oil.  There is no modern style filter but having an after-market oil screen that sits inside the transmission inspection plate is advisable.  Some even have built-in magnets to hold heavier particles

Ford Model T transmission

Modifications to oil system

People who live in mountainous regions often add an external oil line to get oil to the front of the engine which can get dry on long inclines.  People who build Model T racing cars heavily modify their engines – raising compression and replacing parts to enable higher RPMs – may add an oil pump but otherwise this is rarely done.

Ford Model T external oil line

Oil Type- Engine & transmission

The engine and transmission on Model Ts use the same oil.  Ts came from the factory with the equivalent of SAE 20 weight.  The nearest regularly available modern oil is 30W ND (non-detergent.)  But modern oils are superior in every way to what was available way back in the T era.  Many people, especially in cold climates, use multi-weight oils, such as 10-30 or 15-40.  You really can’t go wrong.

Ford Model T lubrication system

Engine Oil Level & Leaks

It’s true to say that all Ts leak oil.  Weeping from around the pedals is normal.  It’s best not to overfill.  However, checking the level is a little different.  There is no dip-stick.  (Unless you get an after-market one.  These are still available from Major T parts vendors.) There are two petcocks on the transmission oil pan on the passenger’s side.  The correct oil level is about halfway between the two.  If oil comes out of the top one, you have enough.  If no oil comes out of the bottom one, you need to top up.  You should carry a spare quart of oil with you at all times.  Some leaks are worse than others.  Owners just have to accept minor leaks but if the oil is gushing out, or even dripping heavily and constantly, you need to find out why.  The starter motor Bendix cover is a good place to start, or the rear main seal between the engine and transmission.  Or a freeze plug.  Or the head gasket.  You’ve got some work to do.

Ford Model T engine oil  level valves

Differential Oil

The T owner’s manual is not specific about what type of oil is optimal for the differential.  Back then, oil was simply classified as light, medium and heavy. The consensus opinion nowadays is that SAE 250 oil is the best for the task.  It is filled via an access nut located in the middle to help avoid overfilling the unit.