Forte Oil Fortifier: every question customers actually ask

Forte Oil Fortifier is an £18 engine oil treatment for older and high-mileage engines that are using oil, dropping oil pressure or blowing blue smoke because the oil film has thinned and worn clearances let it past. It is for petrol and diesel car engines with any crankcase oil including fully synthetic, and it must not be used in a motorbike or any vehicle with a wet clutch.

By Phil Clements, BMW Tool RentalUpdated 16 September 2026

What is it and what does it fix?

An oil restorer, not a cleaner. It thickens the oil film safely and adds anti-wear protection.

Forte Oil Fortifier is an engine oil treatment built around viscosity improvers and anti-wear agents. As oil ages and an engine wears, the viscosity improvers break down, the film gets thinner, and more oil finds its way past worn piston rings, valve guides and bearing clearances. Oil Fortifier replenishes those viscosity improvers so the film is stronger and the oil is safely thicker, which physically reduces how much gets past a worn clearance. Its anti-wear agents lay a protective film on metal surfaces.

That is why it is aimed at three symptoms in older or high-mileage engines: high oil consumption between services, dropping oil pressure (often first seen as a flickering oil light at idle when hot), and blue exhaust smoke from oil escaping past worn rings or hardened valve stem seals. It is a lubrication and conditioning product, so it is not linked to any fault code.

It is not a cleaner. Forte rate its profile as viscosity improvers 5 out of 5 and anti-wear 4 out of 5, but detergents and dispersants only 2 out of 5. If the engine is sludged, Forte recommend cleaning first with Advanced Formula Motor Flush and adding Oil Fortifier to the fresh oil. The full Forte Oil Fortifier product page has the reviews and the order button. See the Forte Seal Conditioner page for the product that pairs with this one.

How do I use it?

The exact method from Forte's guidance. No draining, no tools, no special oil. It is often used alongside Forte Seal Conditioner; the Forte Seal Conditioner page explains when that pairing makes sense.

Add one full bottle through the oil filler capStraight into the existing engine oil. It can be added at any time; you do not need to wait for a service or drain anything first.
Drive normally for a dayOrdinary driving lets it mix fully through the oil system. There is nothing else to do on day one.
If you are treating valve stem seal smoke, add Seal Conditioner on day twoForte's two-step order is Oil Fortifier first, drive for one day, then add Forte Seal Conditioner. The Fortifier thickens the film and slows the leak while the conditioner works on the rubber.
For routine maintenance, add it to fresh oil after a flushForte's sequence for a worn engine is Advanced Formula Motor Flush into the old oil before the change, then Oil Fortifier into the new oil.
Give it two to four weeksQuieter running may be noticed within the first few days. The full restoration effect on consumption and pressure takes two to four weeks of normal driving.

When will it not help?

Phil would rather you kept your £18 than bought the wrong bottle. These are the cases where Oil Fortifier is the wrong product or only part of the answer. The Forte Seal Conditioner page covers the companion product and when to add it.

Wet clutch systems. It must not be used in motorbikes or any vehicle with a wet clutch. The thicker film and anti-wear agents are made for a car engine sump, not a shared clutch bath.
A mechanically broken engine. It reduces how much oil gets past a worn clearance. It does not rebuild piston rings, bores, bearings or a cracked seal. A knocking engine, a dead cylinder or heavy smoke under load needs a diagnosis, not an additive.
A sludged engine on its own. Detergents and dispersants are only 2 out of 5 in its profile. It will not clean out sludge or varnish. Flush first with Advanced Formula Motor Flush, change the oil, then add the Fortifier.
Hardened valve stem seals on its own. It slows the smoke by thickening the film, but the rubber is conditioned by Forte Seal Conditioner. Use both, in that order, for startup and pull-away blue smoke.

Forte Oil Fortifier

The oil treatment for a worn engine that is using oil, losing pressure or smoking blue. Replenishes viscosity improvers and anti-wear protection in the existing oil; add it through the filler cap and drive. Not for wet-clutch motorbikes. Ships worldwide from the UK; UK delivery free on orders of £35 or more, postage and any duty shown at checkout for the USA, Canada, Australia, New Zealand and Ireland.

£18Free UK delivery on £35+ orders

Order Oil Fortifier Full product page

Forte Seal Conditioner

Step two of Forte's two-step treatment for blue smoke on startup and pulling away. Conditions hardened valve stem seals and other rubber oil seals; add it the day after the Oil Fortifier. Not for automatic gearboxes or wet-belt engines. Ships worldwide from the UK; UK delivery free on orders of £35 or more, postage and any duty shown at checkout for the USA, Canada, Australia, New Zealand and Ireland.

£18Free UK delivery on £35+ orders

Order Seal Conditioner Full product page

Oil Fortifier questions, in the order people ask them

My car is burning oil between services. Will Oil Fortifier stop it?

It is made for exactly that. In an older engine the oil film thins and more oil slips past worn rings and valve guides. Oil Fortifier replenishes the viscosity improvers so the film is stronger, which reduces how much gets past. Consumption usually drops rather than stops dead, and the full effect takes two to four weeks.

What causes an engine to burn oil fast?

Worn piston rings, worn valve guides or hardened valve stem seals let oil into the combustion chamber, a failed breather can pull oil vapour into the intake, and thin aged oil makes all of those worse. Oil Fortifier addresses the thin-oil part. It does not replace worn parts.

My oil light flickers at idle when the engine is hot. Is that low oil pressure?

Usually, yes. Hot oil is thinnest, and at idle the pump is turning slowest, so a worn engine shows its lowest pressure there. Check the level first. If the level is right, Oil Fortifier thickens the oil safely and Forte list restoring dropping oil pressure in worn engines as one of its main jobs.

Will it fix low oil pressure caused by a worn oil pump or bearings?

It raises pressure by strengthening the oil film in worn clearances; it does not rebuild a pump or bearings. A sudden collapse in pressure, knocking, or a light that stays on at speed means stop and diagnose. A flickering light at hot idle in a high-mileage engine is the case it is meant for.

Does Forte Oil Fortifier work for blue smoke?

Yes, as step one. Blue smoke is oil burning. Oil Fortifier reduces the amount of oil getting past worn rings and seals by thickening the film. If the smoke is the startup and pull-away kind, that is hardened valve stem seals, and the fix is Oil Fortifier first, then Forte Seal Conditioner a day later. Read the blue smoke page for the five-minute test.

Oil Fortifier or Seal Conditioner: which one do I need?

Ask what the symptom is. Oil consumption, low oil pressure and engine noise point to Oil Fortifier. Blue smoke on startup or after idling, and minor weeps from rubber oil seals, point to Seal Conditioner. Smoke plus consumption is usually both, and Forte's order is Fortifier first, Seal Conditioner the next day.

Is it just an oil thickener?

It thickens the oil safely and for a reason. Viscosity improvers are in your oil from new and break down with age and heat. Oil Fortifier puts them back and adds anti-wear agents, so you get the film the oil had when fresh, not a treacle that starves a cold start.

Will it quieten a noisy engine?

Forte list quieter running as a benefit, often noticed within the first few days, with the full effect in two to four weeks. That is noise from thin oil and worn clearances. A ticking hydraulic lifter is a different problem; see the noisy lifters page.

How do I use Forte Oil Fortifier?

Add one full bottle through the oil filler cap into the existing oil, then drive normally for a day so it mixes through. No draining. If you are treating valve seal smoke, add Seal Conditioner the following day. For maintenance, Forte recommend adding it to fresh oil after an Advanced Formula Motor Flush. Step by step on the Oil Fortifier product page.

Do I have to change the oil before adding it?

No. It goes into the oil that is already in the engine and can be added at any time. The only reason to change the oil first is if the engine is sludged, because Oil Fortifier is not a cleaner; in that case flush, change the oil and filter, then add the Fortifier to the new oil.

How long does Forte Oil Fortifier take to work?

Engine noise may improve within the first few days. Oil consumption and oil pressure improvement build over two to four weeks of normal driving as the treated oil does its work across every clearance. Judge it at the four-week mark, not the first morning.

How much do I need for a big engine, like a 4.4 V8?

Forte's instruction is one full bottle into the existing oil. There is no published extra-bottle rule for this product as there is for Seal Conditioner. Message Phil with your engine if you want to check before ordering.

Can I use it with fully synthetic oil, and in a diesel?

Yes to both. It is compatible with all crankcase oils including fully synthetic, and Forte list it as suitable for petrol and diesel engines. The only stated exclusion is wet clutch systems.

Can I use it in a motorbike?

Not if the bike has a wet clutch, which most do. Forte's caution is explicit: it must not be used in vehicles or motorbikes equipped with wet clutch systems. If your bike has a dry clutch, message Phil before ordering rather than guessing.

Is it safe for a wet-belt engine such as a 1.0 EcoBoost or 1.2 PureTech?

Forte's guidance we hold for this product does not list wet-belt (TBIO) engines either way, so we will not claim it. Message Phil with the engine before adding anything to the oil. Seal Conditioner is stated as not for wet-belt engines; the wet-belt-safe flush is New Generation Engine Flush, see the wet-belt flush page.

Can I add Oil Fortifier and Motor Flush at the same time?

No, they go in at different times. Advanced Formula Motor Flush goes into the old oil for 15 to 20 minutes of idling immediately before the oil is drained. Oil Fortifier goes into the fresh oil afterwards. Doing it in that order is Forte's best practice for a worn engine.

Does it set off or clear any fault codes?

Neither. It is a lubrication treatment with no OBD fault code association. A stored code needs its own diagnosis.

Is Oil Fortifier the same as Forte Oil System Protector?

No. They are different additive profiles for different jobs. Oil Fortifier is the viscosity-and-wear product for an engine that is already using oil or losing pressure. The Oil System Protector vs Oil Fortifier page puts the two side by side.

How much is Forte Oil Fortifier and is delivery included?

It is £18 (a single bottle pays Royal Mail Tracked 48 £3.65 or Tracked 24 £4.65; orders of £35 or more, such as the £36 two-step treatment with Seal Conditioner, ship free) from BMW Tool Rental's Oil Fortifier page. The two-step treatment with Seal Conditioner is £36 for both bottles.

Do you deliver outside the UK?

Yes. UK delivery is free on orders of £35 or more. Orders to the USA, Canada, Australia, New Zealand, Ireland and the rest of Europe are sent tracked from the UK, with postage and any duty shown at checkout before you pay. There is a dedicated page for US customers.