Best Engine Oils for High-Mileage Cars in 2025

If your car's clock is ticking over 100,000 miles (or 160,000 kilometres for the metrically minded), then you’re in high mileage territory. And let’s be honest, once you’re there, you can’t afford to cut corners on maintenance.

One of the biggest favours you can do for an older engine is to feed it the right oil. In 2025, engine oil tech has come a long way, but not all oils are created equal, especially when it comes to high mileage motors.

This guide will give you the lowdown on the best engine oils for older cars in 2025, what to look for on the label, and how to make sure your engine keeps ticking over for another hundred thousand miles.

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What Makes an Oil Right for High Mileage Engines?

High mileage engines have different needs. Years of heat, friction, and wear take their toll on seals and gaskets, and small oil leaks or burn off become more common. That’s where high mileage engine oils step in.

These oils are blended with:

• Seal conditioners to rejuvenate old gaskets

• Extra detergents to clean sludge and varnish buildup

• Viscosity modifiers to maintain oil thickness at high temps

• Anti wear additives like zinc or moly to protect worn components

If your car’s using a bit of oil between changes or you’ve got minor leaks under the engine, switching to a high mileage blend could help.

Top Engine Oils for High Mileage Cars in 2025

Here’s our straight talking rundown of the best options currently on the market. All of these have been tested, reviewed, and found to hold up under real world driving conditions.

1. Castrol GTX High Mileage 10W 40 (Synthetic Blend)

Best All Rounder for UK Roads

Castrol’s been a go to brand in workshops for decades, and their high mileage GTX blend is top notch. This 10W 40 grade is perfect for older petrol engines commonly found in British used cars.

Pros:

✔ Contains phosphorus replacement technology to reduce catalytic converter wear

✔ Fights sludge with premium detergents

✔ Excellent performance in stop start city driving

Ideal For: Commuters with older saloons, hatchbacks, or SUVs

2. Mobil 1 Extended Performance High Mileage 5W 30 (Full Synthetic)

Best for Long Oil Change Intervals

If you're pushing your oil changes to the upper end of the interval (say 10,000 miles or more), Mobil 1’s your mate. It’s full synthetic, built to last, and specifically made for high mileage engines.

Pros:

✔ Designed for engines over 75,000 miles

✔ Excellent thermal stability

✔ Helps prevent leaks and reduce oil consumption

Ideal For: High mileage German cars, long distance drivers, or anyone who hates crawling under the car every few months.

3. Shell Helix HX7 High Mileage 10W 40

Best Budget Friendly Option

Shell’s HX7 High Mileage strikes a great balance between performance and price. While it’s not fully synthetic, the semi synthetic blend offers more than enough protection for the average high mileage car.

Pros:

✔ Great detergent package for cleaning

✔ Improves start up protection

✔ Easy on the wallet

Ideal For: Older Vauxhalls, Fords, and other family runabouts with 100k+ miles

4. Valvoline MaxLife 10W 30 (Synthetic Blend)

Best for Smoother Engine Operation

Valvoline’s been making motor oil since your granddad’s Cortina was new, and they know how to treat an old engine. MaxLife is one of the original high mileage formulas and still one of the best.

Pros:

✔ Contains seal conditioners and anti wear agents

✔ Reduces engine noise in older motors

✔ Excellent cold weather performance

Ideal For: Older imports, classic cars used as daily drivers, or engines with noisy top ends

5. Liqui Moly Leichtlauf High Tech 5W 40

Best for European Performance Cars

If you’re looking after a high mileage Audi, BMW, or Merc, Liqui Moly’s German engineered oil is worth the extra quid. It’s a premium full synthetic with a reputation for smoothing out rough running engines.

Pros:

✔ ACEA and OEM approved

✔ Excellent high temp stability

✔ Ideal for turbocharged engines

Ideal For: High mileage performance saloons and estates that you’re not ready to trade in just yet

What to Look for When Choosing Oil

Aside from brand and blend, here are a few key things to check:

• Viscosity Grade: For the UK, common choices are 5W 30 or 10W 40, depending on your car’s make, model, and how cold it gets where you are.

• API or ACEA Rating: Make sure the oil meets your manufacturer’s spec (check your owner’s manual or the cap under the bonnet).

• High Mileage Label: Oils marketed for 75,000+ mile engines usually contain additives that help with wear and tear.

And don’t forget to check whether your car actually needs synthetic. Older engines that haven’t been rebuilt may do just fine on semi synthetics.

Can High Mileage Oil Fix Leaks?

Let’s set the record straight: No oil will repair a blown head gasket or a cracked block. But if you’re noticing minor weeping from seals, or a bit more blue smoke than you’d like, high mileage oils can reduce the issue. The seal conditioners help soften old rubber, potentially slowing leaks.

But be wary of brands that promise too much. If it sounds like snake oil, it probably is.

How Often Should You Change It?

For high mileage engines, the usual rule is every 5,000 to 7,000 miles (or about 8,000 to 11,000 km), even with synthetic oil. If your car's burning or leaking oil, check the dipstick regularly and top up between changes.

Also worth noting older engines can generate more carbon and contaminants, so don't overextend oil intervals just because the bottle says "Extended Performance".

Final Thoughts

If you’re driving a car that’s seen better days, don’t retire it just yet. With the right engine oil, you can extend its life, keep it running smoother, and maybe even boost fuel economy a bit.

It’s one of the simplest maintenance choices with the biggest payback, especially in 2025, when engine oils are smarter and more specialised than ever.

Look after your motor, and it’ll keep looking after you, high mileage or not.

Mike Floyd

Senior Maintenance Editor, Car Care Column