Oil is escaping from the engine. A weep or a light film is normally an advisory. It becomes a failure when the leak is dripping so badly it could reach the road or a hot component, or where it has contaminated something safety-related like a brake or a suspension bush.
Wording as it commonly appears on an MOT certificate: “Engine has an oil leak”.
What does it mean?
Oil is escaping from the engine. A weep or a light film is normally an advisory. It becomes a failure when the leak is dripping so badly it could reach the road or a hot component, or where it has contaminated something safety-related like a brake or a suspension bush.
How serious is it?
Usually recorded as: Advisory, Major. The tester assesses the actual vehicle on the day, so your certificate is what counts.
What normally causes it?
- A rocker or cam cover gasket — the most common and the easiest to fix
- The crankshaft front or rear oil seal, the rear one usually meaning gearbox-out labour
- A sump gasket or a stripped sump plug thread
- A blocked crankcase breather building pressure and pushing oil past good seals
- Oil filter housing seals, which are a known weak point on several common diesels
What a mechanic would check
Degrease it, drive it, then look with a UV light or fresh eyes — oil always tracks downwards and backwards, so the drip point is almost never the source. I also check the breather system before condemning a seal, because replacing seals on an engine with crankcase pressure just moves the leak somewhere else.
What might need replacing
- A cover gasket or seal
- A sump gasket or a repair insert for the plug thread
- A breather or PCV valve
- Crank seals in the more serious cases
Can you still drive it?
A weep is a watch-the-dipstick job. Check the level weekly and top up with the right grade. If oil is landing on the exhaust — you'll smell it and see smoke off the bonnet — get it fixed before it becomes a fire risk.
Repair cost
Cover gaskets are cheap and quick. Rear crank seals are expensive purely because of access. Diagnosing the actual source first is what stops you paying twice.
Before the retest
Re-check the specific item on your certificate yourself before the retest — catches that latch first time, no fuel smell or drips under the car, doors that open from inside and out. Most of these are inexpensive repairs, so it is worth also looking over any advisories on the certificate while the car is booked in, rather than waiting for them to become failures next year.
Retest rules
If the vehicle stays at the test centre for repair and is retested within 10 working days, a partial retest is often free; some items qualify for a free retest if you bring the car back by the end of the next working day. The exact conditions are set out on GOV.UK, so confirm with the test centre before you leave. A major or dangerous failure means the car cannot legally be driven away unless the previous MOT is still valid and nothing dangerous was recorded — check your certificate first.
Related help
More other mot items failures · MOT failure decoder · Ask a mechanic about your certificate
This is general guidance from a UK mechanic, not a substitute for a physical inspection. Only the tester who inspected your vehicle can confirm what was recorded and why.