It starts with the base oil
Every engine oil is a base oil plus an additive package. Mineral oils use refined crude-oil bases; synthetic oils use more heavily processed or chemically engineered bases with more uniform molecules; semi-synthetics blend the two. More uniform base oil generally means more stable behaviour across temperature extremes and longer resistance to breakdown.
Practical differences
The deciding factor is still the specification in the vehicle handbook. If the engine calls for a modern low-viscosity specification, a suitable synthetic is usually required. For an older engine specified on 10W-40 or 15W-40, a quality semi-synthetic or mineral oil that meets the required API/ACEA level does the job.
- Synthetic oils typically hold their protective properties longer between changes.
- Semi-synthetics balance cost and performance for everyday driving.
- Mineral oils remain appropriate where the manufacturer specifies them, at shorter intervals.
A note on oil-change intervals
No base oil excuses skipped maintenance. Dusty roads, dense traffic and high temperatures — all common in Bangladesh — are 'severe service' conditions in most handbooks, which usually means shorter intervals than the maximum printed number.
Need help choosing?
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