Spread filters in EAs: fixed thresholds or relative ones?

[FXS London Scalper]

Many EAs include a spread filter to avoid trading when spreads are wide. A fixed maximum, such as 2 pips, is simple but may block trades on pairs with naturally wider spreads or allow trades when the spread is unusually wide for a tight pair.

An alternative is a relative filter: compare the current spread with a rolling average for that pair and time of day, and skip trades when the current spread is, for example, twice the average.

A worked example: on EURUSD the typical spread at 10:00 might be 0.2 pips. A fixed filter at 2 pips would allow trading at ten times normal. A relative filter would catch this.

The downside of relative filters is complexity. The EA must collect spread data over time, which requires logging or a startup period.

For most EAs, a fixed threshold per pair, set from observed typical spreads, is a reasonable middle ground.

Which approach do you use for spread filtering?