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How Serious Is It?
| Situation | Risk Level | Action |
|---|---|---|
| Wrong grade (e.g., 5W-30 instead of 0W-20) | Medium | Change at next service or sooner |
| Wrong spec (e.g., non-DPF oil in DPF car) | High | Change immediately |
| Mineral in a synthetic-required engine | Medium-High | Change within 1,000 miles |
| Petrol oil in a diesel engine | High | Change immediately (DPF risk) |
| Diesel oil in a petrol engine | Low-Medium | Change at next service |
Recommended Engine Oils
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What to Do
If you’ve used the wrong oil:
- Don’t panic — short-term use of the wrong oil rarely causes immediate damage.
- Identify what oil was used and what your car actually needs (use our oil finder).
- If the spec is wrong for a DPF diesel, change the oil as soon as possible.
- If just the grade is slightly off (e.g., 5W-30 vs 5W-40), change at the next service.
- If you’ve driven less than 100 miles on the wrong oil, a drain and refill is all that’s needed.
Frequently Asked Questions
Will the wrong oil void my warranty?
Potentially, if the manufacturer can show engine damage was caused by incorrect oil. Keep receipts showing the correct oil specification for all future services.
Can I mix different brands of engine oil?
Yes — mixing brands of the same grade and specification is fine. The oil industry uses compatible additive packages.
Can I mix 5W-30 and 5W-40?
In an emergency top-up, yes. The result will be approximately 5W-35. Change to the correct grade at the next service.
Recommended Products
How we check fitment for this guide
We cross-reference fitment figures against manufacturer specifications and OE-supplier catalogue data where available, and matched to the standard codes that actually govern fit — battery type/group sizes, wiper lengths and fitting types, bulb fitment codes, tyre size markings, and oil specifications. We work by make, model, year, engine, and build date, because a single model can take different parts across its life. Where the right part depends on your exact vehicle, we tell you to confirm by registration or VIN. More on our method →