Should the Forester use 30 or 40 engine oil?
3 Answers
The Forester uses 30 engine oil, which has relatively low viscosity and is suitable for Japanese cars like the Forester with precisely constructed engines. 40 engine oil has higher viscosity and is more suitable for German or American cars. Engine oil, also known as motor lubricant, serves functions such as lubrication and friction reduction, auxiliary cooling, sealing and leak prevention, rust and corrosion protection, as well as shock absorption for the engine. The Forester is a compact SUV produced by Subaru, with dimensions of 4640mm in length, 1815mm in width, and 1730mm in height. The Forester offers options including a 2.0L hybrid system, a 2.0L naturally aspirated engine, and a 2.5L naturally aspirated engine.
I've been driving a Subaru Forester for several years. Initially, I tried 40-weight oil but noticed significantly higher fuel consumption and sluggish acceleration. Later, I checked the owner's manual which clearly recommends 5W-30 or similar low-viscosity oils, with 0W-20 being more suitable for newer models. After switching to 30-weight oil consistently, the engine runs much smoother and fuel consumption returned to normal levels, saving about 1-2 liters per 100 kilometers. This really depends on your specific model and year - mine's a 2015 with a boxer engine that maintains performance even in high temperatures or prolonged traffic jams. Never arbitrarily switch to higher viscosity oils unless a professional has assessed wear conditions. For routine maintenance, just choose quality full-synthetic oil from reputable brands and check oil levels every 5,000 kilometers - it's both worry-free and cost-effective.
As someone who frequently deals with car issues, the Forester commonly performs better with 30-weight oil. The standard recommendation is SAE 5W-30, which is the factory specification for most models—it ensures good fluidity during cold starts, reducing engine wear. However, if your car has over 100,000 kilometers or shows minor oil leaks, 40-weight oil can be a temporary solution, but you must check oil pressure and the filter. I've used tools to test some cases where incorrect oil caused a 15% increase in fuel consumption and long-term engine damage. Always refer to the manual or consult a professional shop during maintenance. Don’t delay oil changes—synthetic oil lasts longer, but sticking to the manufacturer’s recommendations prevents costly overhauls.
