Manufacturer "acceptable" oil consumption is shockingly high — many UK car makers consider up to 1 litre per 1,000 miles "within tolerance". Anything significantly above that is a real problem.
How much oil use is actually normal?
Modern engines are allowed to use oil, and manufacturers publish limits that surprise most owners. Many mainstream makers state up to one litre per 1,000 miles as acceptable; BMW and some VAG performance engines have quoted figures around that mark for years, and dealers will point at the handbook rather than repair the car. What matters more than the absolute number is the trend. An engine that has always used half a litre between services and still does is fine. One that used nothing last year and now needs topping up every 800 miles has developed a fault. A sensible way to judge it: under 0.5 litre per 1,000 miles is normal on most engines; 0.5 to 1 litre is high but often within the maker's limit; more than a litre per 1,000 miles means something is wrong and should be investigated before it becomes an engine rebuild. Check it properly, too. Level ground, engine warm, switched off for at least five minutes, dipstick wiped and reinserted fully. A reading taken straight after a motorway run will always look low.
Burning it or leaking it — how to tell in five minutes
Every case falls into one of two camps and they are easy to separate. **Leaking.** Park on clean cardboard overnight. Fresh engine oil is amber to light brown; old oil is nearly black. Look at the front of the engine for a cam cover gasket weep, at the back for a rear crank seal, at the sump gasket and drain plug, at the oil filter housing, and on turbo diesels at the turbo oil feed and return pipes. Oil blowing back along the underside of the car after a motorway run points to a leak higher up than you would expect. **Burning.** No drips, but oil disappears. Blue-grey smoke, worst on start-up, when lifting off after a long downhill, or under hard acceleration. Spark plugs come out black and oily. The exhaust tip is sooty and wet rather than dry grey. The reason this matters: a rocker cover gasket is a £120 job, and piston rings are an engine out.
The usual causes on UK cars
**Worn valve stem seals.** The signature is a puff of blue smoke on start-up or after idling at traffic lights that clears once you get moving. Oil seeps down the valve guides while parked. Common on higher-mileage petrol engines. **Worn or stuck piston rings.** Blue smoke under load, oil use that climbs steadily, and often lower compression on one or two cylinders. Some engines — the EA888 1.8 and 2.0 TSI, certain Subaru and Mini engines, some BMW N47 and N20 units — are known for rings coking up rather than physically wearing, and a decoke or ring replacement is the fix. **PCV or crankcase breather failure.** Frequently the cheapest real fault. A blocked or split breather pressurises the crankcase, forcing oil past seals and up the intake. It often shows up as a sudden increase in oil use, a whistle from the engine, and oil residue in the intake pipework. £80 to £350 to fix and worth checking before anything drastic. **Turbo seal failure.** Blue smoke on overrun and at idle, oil in the intercooler pipes, sometimes a whining turbo. Ignore it long enough and a diesel can run away on its own sump oil, which destroys the engine. **Wrong oil grade.** Putting 10W-40 in an engine designed for 0W-20, or a cheap non-approved oil in a modern low-SAPS diesel, genuinely increases consumption and can also clog a DPF. Always match the manufacturer specification, not just the viscosity.
What a garage will do to find it
A proper diagnosis runs in this order and normally costs £60 to £150: 1. **Confirm the rate.** Fill to the top mark, note the mileage, drive 500 to 1,000 miles, measure the top-up. Everything else is guesswork without this number. 2. **UV dye and inspection.** Dye in the oil and a UV lamp finds a leak that spray and road grime have hidden. 3. **Compression and leak-down test.** Separates ring wear from valve or gasket problems and tells you which cylinder. 4. **Crankcase pressure check** to test the PCV system before condemning anything internal. 5. **Borescope through the plug holes** to look at bore condition and piston crowns without stripping the engine. 6. **Coolant check** — oil use with mayonnaise under the cap or coolant loss is a different, more serious conversation.
UK repair costs in 2026
Fitted prices at an independent garage, including VAT: - Cam or rocker cover gasket: £120 to £320 - Sump gasket: £180 to £450 - PCV or breather system: £80 to £350 - Oil filter housing gasket: £150 to £400 - Turbo seals — realistically a replacement turbo: £700 to £1,800 - Valve stem seals: £600 to £1,400 depending on whether the head must come off - Rear crankshaft seal, gearbox out: £500 to £900 - Piston rings or an engine rebuild: £1,800 to £3,500 and up - Used or reconditioned engine fitted: £1,500 to £4,000 On an older car the honest maths is often to keep topping it up. A litre of decent oil every 700 miles is roughly £8 to £14 — several years of that still costs less than a rebuild. What you must not do is let it run low.
The damage you are risking
Running an engine low on oil is the fastest way to destroy it. Oil pressure drops, the big-end bearings are starved, and once they knock the engine is finished. The oil pressure warning light is not an early warning; by the time it lights the damage may already be under way. Burning oil also has knock-on costs. Oil ash blocks a diesel particulate filter, so a car that burns oil will need forced regenerations and eventually a new DPF at £900 to £2,200. On petrol cars it poisons the catalytic converter and coats the lambda sensors, causing fuelling faults and an MOT emissions failure. So whatever you decide about repairing it, buy the right oil by the five-litre can, keep it in the boot, and check the dipstick every single fuel fill. Set a phone reminder if you are the type to forget — the people who lose engines are almost never the ones who check weekly.
MOT and emissions
There is no MOT check for oil consumption itself, but there are two ways it fails you. Visible blue smoke is a fail under the visible smoke rules, and on a diesel the smoke opacity meter picks it up immediately. An oil leak dripping onto the road or onto hot exhaust components is also a fail — a weep is advised, an actual drip is refused. If the oil use has fouled the catalytic converter, the gas test will fail too, and that repair costs more than most of the fixes listed above.
How much oil should a car use between services? — Under half a litre per 1,000 miles is normal on most engines. Half to one litre is high but often within the manufacturer's stated limit. More than a litre per 1,000 miles means there is a genuine fault worth investigating.
Why is my car using oil but not leaking? — It is being burnt. The usual causes are worn valve stem seals, worn or coked piston rings, a failed crankcase breather, or leaking turbo seals. Blue-grey smoke under load or on start-up confirms it.
Is it cheaper to keep topping up than to repair? — Often, yes, on an older car. A litre of good oil is £8 to £14 against £1,800 or more for a rebuild. The rule is simply that you must never let the level fall below the minimum mark — that is what actually kills engines.
Can the wrong oil make my car use more? — Yes. Using a heavier or non-approved grade in an engine designed for a thin low-SAPS oil increases consumption, and on a diesel it also loads the particulate filter with ash. Always match the manufacturer's specification, not just the viscosity number.
What does blue smoke from the exhaust mean? — Burning oil. On start-up only, suspect valve stem seals. Under acceleration or load, suspect piston rings. At idle and on overrun with oily intercooler pipes, suspect the turbo seals.
Will high oil consumption fail an MOT? — Not on its own, but the blue smoke it causes is a visible smoke failure, and an oil leak that drips rather than weeps is also a failure. If the oil has damaged the catalytic converter, the emissions test will fail too.
How often should I check the oil if my car uses some? — Every fuel fill, and always before a long motorway run. Check on level ground with the engine warm but switched off for five minutes, wiping and reinserting the dipstick fully.
Can a blocked breather cause oil loss? — Very much so, and it is one of the cheapest faults to fix. A blocked PCV or crankcase breather pressurises the engine and pushes oil past seals and into the intake. Check it before agreeing to any internal engine work.